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GEOLOGY

How did the marble form?

Mostly likely the original limestone formed in shallow, near-shore, tropical waters on top of a seamount (old sunken volcano with a crew cut) associated with a fore-arc basin, similar to the ocean side of the Japanese island arc. The limestone was then buried under other rocks and partially subducted under the western part of the North American plate, where it was metamorphosed (recrystallized) into marble most likely when a younger and therefore hotter back-arc basin was thrust under it. Some metamorphism was also due to contact with intrusive igneous materials but this appear limited to the first fifty feet or so of the contact with the biggest part of the Grayback Pluton.

What are 3 good examples of igneous, metamorphic and sedimentary rocks inside and outside the cave?

Igneous: Basaltic Dike in the Ghost Room; Gabbro (Big Tree Trail)

Metamorphic: Marble (inside the cave and all over the hillside); Serpentinite (outside the cave on the driveway from lower parking lot)

Sedimentary: Limestone (all of the stalagmites, stalactites, and flowstone are made of limestone in the cave); Loess (glacial dust—can be seen on the ceiling from the platform before the metal stairs to Paradise Lost); Chert (it’s been slightly altered, but layers can be seen in the marble of the caves and as folded layers in the lower parking lot); finally, visitors can see lots of “future” sedimentary rocks inside the cave and outside (point them to clays, (all over the cave) sands, and gravels (mostly near the river) in the cave and to the gravels in the river outside the cave or sediments on the hill. You can tell them that sedimentary rocks form when pieces of old rock are again solidified into rocks by heat, pressure, and/or minerals gluing them together. HH and SG

What is the temperature in the cave?

Temperature in Oregon Cave averages about 41 degrees (F.). Unlike Oregon Cave, temperature differences within caves without substantial entrances are very minor because of the insulating properties of rock. A 30°C temperature fluctuation throughout the year above ground can be reduced to 1°C at a depth of 11 meters or about 36 feet (Moore and Sullivan, 1975). However, because of strong airflow through the cave, temperatures even away from the entrances range from the mid-thirties to the low fifties.

In part because of cave entrances, especially entrances located at different elevations, the difference in air temperature between the highest and lowest parts of Oregon Cave is about 9 degrees F. This contrasts with a cave water temperature difference of 2 degrees F. The greater temperature variation of the cave air compared to the cave water is largely the result of the exchange of surface and cave air as a result of both barometric and temperature differences between surface and cave air. A higher percentage of the water compared to the air comes in contact with the rock, and it is the rock which ‘holds’ the temperature.

Where does the water come from in the Cave?

Most of it comes from vertical cracks that go to the surface and some of it comes down along bedding planes (as in the Wedding Cake Room). Water chemistry suggests that most of the water comes seeping through the overlying metamorphosed mudstones until it reaches the marble layer at which point dome pits formed that send water into the cave. Dye tracing indicates that part of the stream (increasingly so % wise as the summer progresses) derives from upper Cave Creek, which descends into the cave through a crack upstream from the Chalet (visitor center). Cave Creek in turn is derived from snowmelt in part from the largest meadow on the surface. The exact source of the upper part of the stream (Ghost Room) is unknown. However, the abundance of metamorphic and volcanic rock in stream deposits in the Ghost Room suggests the origin lies beyond the relatively small block of marble in which the Cave lies. Minor streams flow from the domes in the south end of the cave, through the South Room and Shovel Room, through the South Ghost Room Annex to the Stream Grotto where the Waterfall Passage stream joins, and then to Jules Verne's Well. There the water eventually enters the River Styx.

Are there seasonal fluctuations in the amount of water coming into the cave?

Yes, it tends nowadays to peak in May. The part of the cave closest to the surface dries out in summer while that part 150’ or lower tends to remain wet year round due to how long it takes for water to drain that far. Some of the deepest water and that along the bedding planes probably takes at least a year if not many years to reach those areas of the cave. Less water flows in the stream in late summer or early fall than at any other time of year.

Does more water pour in through the walls and ceiling when the snow is melting and/or there is heavy rainfall?

Yes, water filters through the mountain to the cave and the cave is affected by changes on the surface. According to a report from Michael Sims (from the 70’s) the flow of the River Styx increases 24 to 36 hours after a rainstorm.

What natural occurrences would prevent a cave from continuing to form? (ie, drought or a forest fire)

The biggest one is drought, no water getting into the cave means no formation growth. A forest fire is good for growth in a cave. Less vegetation on the surface means that more water can get into the cave.

Where/ how exactly does the water pick up calcium?

Marble is made up of the mineral calcite: CaCO₃, so there is calcium in the marble. The marble used to be limestone and limestone was once dead sea-creatures, whose shells were made up of calcium. Fresh rain water flows through the surface soil and meets up with the marble. It slowly finds a crack and flows into that crack, eroding the marble and therefore picking up trace amounts of calcium (Ca) and carbonate (CO₃), which can later be deposited as a stalagmite or stalactite. HH

Does marble ever “exhaust” to the point where the water is unable to pick-up calcium in the areas it has travelled through time and time again?

No, when there is no more calcium left there is no more rock left.

What does stalagmite and stalactite mean (the root meanings of the words)?

There seems to be some discussion over exactly what word or words stalagmite and stalactite are derived from. There seems to be agreement that both words are derived from Greek words associated with the word “drip.” According to Origins by Partridge Staff and Eric Partridge, they are associated with the Greek words stalaktos (dripping), stalagmos (a dripping), and stalassein (to drip).

How fast do these stalactites grow?

The simple answer, keeping in mind that it fluctuates widely over time and from place to place in the cave, is about 1 inch per 1000 years. Actively forming soda straws in Oregon Caves grow about a tenth of an inch to an inch per one thousand years. The flowstone and dripstone sampled by Turgeon (2001) in Oregon Caves showed growth rates between 1.54 to 31.5 millimeters (about .06 inch to 1.24 inches) per thousand years during early to mid-interglacial periods of the last 500,000 years. Vacco’s thesis shows a growth rate from 8.5 to 20 mm (.3”-.79”) per 1000 years in the period from ~13.5 to 9.5 thousand years before present, indicating faster growth during the interglacials compared to the glacials.

Since <1% of the soda straws in Oregon Caves show any regrowth, the average is <.0014”/century or around .015”(.032mm) per 1,000 years. Lehman Caves has similar regrowth rates. The difference between these growth rates probably means that with global warming and fire suppression, the growth rate in Oregon Caves has slowed down considerably (perhaps down a thousand fold). Increases in both temperature and water film thickness (related to precipitation) increases growth in the Caves (Turgeon 2001).

How old are the secondary formations (speleothems)?

The larger formations are half a million to tens of thousands of years old for. The translucent tips of soda straw stalactites are less than 10,000 years old.

What is this knobby stuff (cave popcorn)?

Cave popcorn usually forms through a combination of evaporation and loss of carbon dioxide. Cold air, especially during winters, nights, and glacial periods, flows into the cave. As it moves into the cave, the air warms up and is therefore able to evaporate more water. This air is, relative to other cave air, lower in carbon dioxide. Therefore, more carbon dioxide is going to be lost to this air from water in the cave in order to equalize the difference.

As you move down the passage you will find that more popcorn forms on the sides facing you than on the opposite sides. This is probably because dry air flow generally moves from the 110 Exit to the Ghost Room and beyond to upper levels of the cave. This air flow evaporates water and causes precipitation of cave popcorn on the upwind side of stalagmites, as at Niagara Falls. At least at one time, there were probably one or several natural entrances to Oregon Cave higher than the 110 Exit. The resulting chimney effect moved air through the cave that helped deposit much of the cave popcorn through evaporation and loss of carbon dioxide.

Studies in Carlsbad indicated that about 40% of the deposition of some speleothems was due to evaporation and about 60 percent was due to carbon dioxide loss. However, the amount of evaporation is probably less for Oregon Cave than for Carlsbad.

Why is that formation on the ceiling (of Miller's Chapel or Ghost Room) so white?

Pure calcite is clear or translucent, but air or water bubbles or changes in crystal orientation cause them to turn white. The more recent, deeper formations in the cave are white because organics and dissolved iron often don't get this far into the cave and possibly because the iron in the rocks has not had time to oxidize enough to darken the rock.

A change from translucence to whiteness is probably due in part to loss of water that reveals the air bubbles and/or solution along crystal boundaries. Air bubbles and pockets are also why milky quartz, most ice masses, waterfalls and white hairs are white. Only when glacial pressures squeeze most of the air pockets out does ice attain its transparent, blue color.

How fast does moon milk grow?

Rate of growth is quite variable. However moon milk in the 110 Exit produced in the nineties at least a 1/10 of an ounce from nine foot square surfaces during a winter season, which is when most of our active moon milk formed. There seems to be very little growth in the last decade or so perhaps because warmer outside air in winter can no longer evaporate as much water when it enters the cave and warms up, thereby lowering its relative humidity.

“Flowstone” happens when calcite deposit flows over the rock, but how can we explain the deposits that hang off the wall, like in Paradise Lost. Is there actually rock underneath there too?

While most of the hillside is marble, there are also some Chert layers. Chert is silica-rich rock made from radiolarians. Chert, unlike calcite (mineral making up marble) does not dissolve as easily in carbonic acid. So chert ledges stick out of the marble wall. When water falls on these ledges, it formed flowstone and stalagmites. Eventually so much limestone was added the original rock ledges are no longer visible. (see diagram)

Please explain the difference between the regular flowstone and the flowstone that glows.

While the flowstone that makes up Angel Falls consists of the same mineral (calcite) as the flowstone in the rest of the cave, it also contains small amounts of fulvic acid (aka Soil Juice). The fulvic acid is derived from plant roots and decaying vegetation from the surface. The electrons are put into a ‘higher energy’ state when the black light is turned on. HH

Please describe fulvic acid (aka soil juice) in more detail.

C₁₃₅H₁₈₂O₉₅N₅S₂is the chemical formula. Fulvic and humic acid is a result of chemical and biological degradation of dead plants and animals. Humic acid/extract can be extracted from any material containing well-decomposed organic matter - soil, coal, composts, etc. Extraction is by way of treatment of these materials with a solution of sodium hydroxide. This dissolves much of the organic matter present. If we then take this solution and add enough acid to drop its pH to about 2, organic material will begin to flocculate and can be separated from the liquid portion. The flocculated material is humic acid. What remains in solution is fulvic acid.

Please describe the electron reaction within the fulvic acid flowstone in more detail.

When the black light is turned on, the electrons inside the formation start to get excited. Its like giving a kid a sugar cookie, the excitement of getting it, eating it and the crash after. When you first turn the black light on nothing really happens, that’s the kid getting the cookie. When the blue color starts to appear the electron are getting into a higher energy state, the kid eating the cookie and having a sugar rush. After the light is turned off the electrons don’t have that energy feeding them anymore and settle back down into a low energy state, the kid after the sugar rush has crashed.

Why does the white flowstone have more air bubbles?

[Insert answer here]

Why do some parts of the white speleothems in the Souvenir Room glow red under a black light?

Many of the formations in the Souvenir Room have been marked with a fluorescent paint that glows red under a black light. This is then used to monitor the growth of the formations and to keep track of any additional damage that might occur.

What created the jutting wall by Paradise Lost?

Differential erosion of chert layers versus marble layers. Basically layers of chert within the marble do not erode as fast as the marble itself.

How did it (Inside-out-Gopher Hole) form?

It likely is a root cast now enclosed by limestone and then moon milk that has largely hardened into more limestone.

Is the chert metamorphic?

The chert that we have is a meta-sedimentary rock, which means that it was once sedimentary, but it has had heat and pressure applied to the rock to make it metamorphic.

Why are boxwork and cave ghosts considered speleogens and not speleothems?

Speleogens are formed by the weathering, water erosion and wind erosion. Examples are current markings, potholes, scallops, rock mills and rock pendants. Speleothems are cave formations by secondary deposits. Examples are stalactites, stalagmites and flowstone. HH

What is the Red Stuff Painted in the Caves?

Well the answer depends on what part of the cave you are referring to. Here are a few possible explanations.

In Miller’s Chapel, pinkish colored stuff, which looks like cement or rock can be seen on the walls in a few places. This is left-over cement from the CCC renovations in the caves. In a few places, red algae can be seen growing on the walls. The lighting system has allowed non-native species survive in the cave by providing heat and light (this is why we turn off the lights at night—to minimize the impact of the lights.

The red stuff on the walls and flowstone are most likely minerals that have been oxidized, similar to rust forming on an old car. Most are probably iron bearing minerals. So it’s pretty much just rust as can be seen in the exit tunnel. HH

How old is the cave?

Based on the radiometric and oxygen isotope age determined by Dr. Turgeon, the oldest speleothem (secondary formation) in the cave is about half a million years. Based on relatively fast erosion of caves in steep sided mountains, that means the cave itself probably is somewhere from half to several million years old. However, the cave could have formed in a much flatter area before recent uplift in the last ten thousand years, based on stream gravels at 1600’ in Cave Junction. If that is the case, Oregon Caves could be quite a bit older. Part of the Cave may have formed before the deposition of gravel at an elevation from near 2,000 feet to 4,000 feet in the Siskiyou’s. The gravel deposit is probably several million years old.

Since the present-day cave most likely formed when much greater amounts of water were entering the marble during interglacials, the most likely time for the formation of the present-day cave was the Bramertonian Stage which lasted from about 1.3 to 1.6 million years ago. Since glacial cycles tend to be about twice as long as the interglacials, it is less likely that the formation of the present cave occurred in more recent (.6-.8 mya) or older (2.1-2.5 mya) interglacials. However, given that the marble beds stick into the mountain at a steep angle, it is likely that an older part of the cave existed that has now been eroded away. This would help explain why we have so many endemics only known from Oregon Caves and why one DNA study indicates that a grylloblattid is at least 2 million years old. Once the water level was below the cave, most enlargement of the cave stopped, and decoration then began.

Some caves in the world may be several hundred million years old as they undergo a new cycle of erosion after being mostly filled in by sediments from an advancing ocean, etc. But the oldest caves in the present cycle of erosion are very large caves with many multiple levels (such as Mammoth) or caves that form very deep underground (such as Lechuguilla, Jewel Cave, Wind Cave, and Carlsbad Caverns). Sections of these caves range from a few million to tens of millions of years old. A large number of theoretical, laboratory and field studies indicate that it takes about ten thousand years to develop big enough holes in limestone or marble that people can crawl through.

The yearly erosion rates of many limestone or marble areas around the world have been measured. Assuming the erosion rates of mid-latitude areas with the same precipitation as Oregon Caves would be similar to Oregon Caves, the ground surface erosion rate would be .00005 meters per year. Since the deepest part of the Caves (Ghost Room and nearby areas) is about 50 meters below the earth's surface, it would take about a million years for the cave to be mostly destroyed.

The wider the crack, the higher the water pressure (hydraulic gradient), and, to a lesser extent, the shorter the flow path, and the higher the carbonic acid, the sooner breakthrough occurs the start of turbulent flow and subsequent faster enlargement of protocaves and then caves). Because of rapid erosion, faulting, and uplift and uncovering of the marble, release of pressure likely caused fairly wide cracks (>.2 mm.) in vertical joints near the surface. These shallow passages, like the Belly of the Whale, would have taken up to several tens of thousands of years to form.

However, most of the cave is deep with long water flow paths along steeply dipping faults and bedding planes that probably had narrow cracks due to overlying pressure (little overburden pressure if cracks are vertical). These may have taken several hundreds of thousands of years to enlarge to the breakthrough time. It typically takes about three to five thousand years for cracks between .5 and 5 millimeters to enlarge by solution during the karstic phase known as initiation. This is somewhat less than the average width of present-day fractures deep in the Monument, mostly because the larger cracks were those that formed cave passages. Likely the bedding planes best suited for cave development were those that faulted when one rock layer slid over another, thus providing the widest or most initial cracks that were parallel to most of the water flow.

Further cave enlargement probably occurred at a rate of about one to two feet every thousand years. With a width of about 100 feet, large rooms like the Ghost Room may have taken about 100,000 years to get to its present size, or a maximum of from 1.7 million to 100,000 years for a typical groundwater cave with this size passage (Dreybrodt & Gabrovsek 2000; Palmer 1991; Ford 2002). The addition of sulfuric acid from oxidizing pyrite found in faults or other fractures that run through the Ghost and South Rooms would have decreased how long it took these rooms to form. Extension of the Caves to its current five kilometers probably took from 50,000 to 100,000 years (Palmer 1984). If the stream exiting the Cave had as much dissolved marble (calcite) as it does today, it would have taken about 200,000 years to dissolve out most of the cave. Since solution generally is much slower at the birth of a cave, more time would have been needed for the Cave to reach its present size. If surface erosion rates resemble does of similar areas, then about 70 feet of rock has been removed topside since the oldest remaining flowstone was deposited. This erosion constrains the upper age of the present cave. Adding all this to the age of oldest flowstone, and one can reasonably say that the age of the present-day Caves is about one to two million years.

Since the present-day cave most likely formed during an interglacial the most likely time for its formation was the Bramertonian Stage which lasted from about 1.3 to 1.6 million years. Since glacial cycles tend to be about twice as long as the interglacials, it is less likely that the formation of the present cave occurred in more recent (.6-.8 mya) or older (2.1-2.5 mya.) interglacials. However, given that the marble beds stick into the mountain at a steep angle, it is likely that an older part of the cave existed that has now been eroded away. This would help explain why we have so many endemics only known from Oregon Caves.

Caves much older than the present-day Oregon Caves do exist. However they usually are protected from erosion by thick layers of overlying rock either in a cave forming from the bottom up, like Carlsbad, or where there are low river gradients and/or resistant cap rocks, as in Mammoth. Grottoes (the remains of caves) can be seen on the walk between the Cave and the main parking lot. Based on rates of slope retreat estimated from rock fall and solution rates, they could be several million years old.

Most cave limestone (flowstone/depositional formations) are impervious to water (unlike many limestones formed in the ocean or on the surface). They usually lack fragments of past rocks and are mostly protected from erosion. All this makes for good radiometric dating, a process by which radioactive elements are measured to determine the age of an object.

For limestone, most geologists use the radioactive metals thorium and uranium. Thorium is almost completely insoluble in water. Uranium is much more soluble. Therefore, when the flowstone deposited, it mostly contained uranium (assuming no rock fragments). The uranium breaks down into thorium at a known, steady rate. Measuring the ratio of the thorium and uranium gives the age of the flowstone, the oldest date here being about 330,000 years. In some of the oldest layers in the Cave, there's not enough uranium in the rock to date it by this method alone. Instead, oxygen and carbon isotope ratios were matched to ratios in ocean cores. This method calculated that the oldest known speleothems in Oregon Caves began about 516,000 years ago. The ratios are largely affected by differences in evaporation rates during glacial and interglacial periods. If there has been little evaporation in cave speleothems (as appears to be the case at Oregon Caves), then the ratios of carbon and oxygen help determine the water temperature, which is the main part of an ongoing paleoclimate dissertation study being done by Lica Ersek from Oregon State University.

There are other ways to date cave sediments although none of these except radiocarbon on bone deposits have been done at Oregon Caves. Cosmogenic nuclide dating (jokingly called “suntan dating”), derives its name from cosmic rays. Quartz is composed of silicon and oxygen atoms. When neutrons and muons from these rays hit silicon nuclei in rocks, one proton and a neutron may be knocked loose to produce an unstable radioactive isotope of aluminum (²⁶Al with a mean half-life of 700,000 years). If an oxygen nucleus is hit, four protons and two neutrons may be lost, creating a radioactive isotope of beryllium (¹⁰Be, half-life of 2.2 mya). ²⁶Al is produced six times faster than ¹⁰Be. When quartz grains enter a cave, the inherited radioactive isotopes decay at different known rates and therefore changes in this ratio yields the time that both isotopes were no longer being produced, ie., no longer exposed to the sun. The ratio between the two decreases over time because the aluminum isotope decays faster than that of the beryllium. Cosmogenic dating has been used to date sediment burial over the past 5 million years, a much longer time frame than thorium-uranium or radiocarbon methods.

Flowstone and dripstone often fluoresce with a black light shining on it, like at Angel Falls. Phosphorescence is luminescence in which a stimulated substance emits light after the external stimulus ends. Electrons move to higher energy levels and then slowly fall back to their former orbits, emitting characteristic wavelengths of light. The thinnest lines, visible only under a microscope, appear to record changes in calcite deposition during individual days and so are far better than tree rings in reconstructing past climates. That’s because the lines are hundreds of times more detailed, are correlated with the two main climate factors (temperature and precipitation), and are up to ten times as old (up to half a million years).

Formation growth rates depend partly on the amount of water dripping into a cave (Shopov et al. 1996) and/or (in the case of Oregon Caves) the water film thickness (29% of growth variability), which likely amounts to much the same thing.

The degree to which the ultraviolet activates the glow in the formations depends mostly on the amount of calcium salts of fulvic acid. Calcium salts of humic, huminomelanic acids, and organic esters contribute a lesser amount of luminescence.

The amount of acids released from roots roughly correlate with sunlight (the solar constant) while the amount released by dead plant matter correlates with soil temperatures and water ratios which in turn are partly controlled by air temperatures in forests. The brightness of the flowstone here indicates it formed under conditions of moderate precipitation and relatively warm temperatures. Too much water dilutes the amount of fulvic acid incorporated into the speleothems (Beynen 1999: 98).

Warmer temperatures also make it more likely the ground will be unfrozen and water therefore can flush in more fulvic acid. During cold periods there is so little organic matter or precipitation (offshore winds) that hardly any dissolved calcite is carried into the Caves.

Speleothem studies indicate that changes in the solar constant, in a cycle of 11,500 years, is equal to climate effects caused by the orbital variations thought to be responsible for glacial/interglacial cycles. Luminescence records with resolution of several years can be correlated with sunspot activity (higher incoming solar infrared and soil temperatures) and the atmospheric production of carbon 14. Records with a resolution of 100 years or less can be correlated with global climatic signals. Cycles of solar activity and insolation with periods of 1, 2, 11-22, 55, 95, 180, 300, 400, 600, 900, 1200, 2300, 3350, 5000 and 16,900 years can be detected by luminescence studies of speleothems (Shopov et al. 1998).

What are the different types of dating techniques for ORCA?

Radiocarbon dating determines the age of carbonaceous materials (materials that contain a lot of carbon) up to about 60,000 years.

Uranium/Thorium (U/Th) dating is commonly used to determine the age of carbonate materials such as speleothems or coral. This method calculates an age based on the degree to which equilibrium has been restored between the radioactive isotope thorium-230 and its radioactive parent uranium-234 within a sample. HH

Radiocarbon dating has been used on burnt wood that was washed into the cave after a fire, while U/Th has been used on formations.

What are the compositions of the igneous intrusions in the cave?

Good question. There has been little detailed study on the intrusions in the cave and interpretations of the intrusions have varied through time. They have been called igneous and clastic intrusions, but there are probably both types in the cave. Sarah Glancy conducted a GeoCorps project on these intrusions in order to characterize their composition and relations based on field work, study of hand samples, and thin section analysis. Here are her findings:

There is a wide range of composition of intrusions in the cave, from intermediate composition or diorite intrusions to dikes/veins that are almost 90% quartz. One may be clastic rather than truly igneous. There seems to be a complex history of intrusions. In at least one area, basalts may have intruded into the marble a long time ago when the rock was originally forming, or early in its history and been metamorphosed to actinolite bearing green rocks as the marble was metamorphosed (however, this conclusion is tentative and requires further investigation). The quartz veins/dikes appear to be cut by intermediate and/or clastic dikes, indicating that the quartz dikes were younger (verify this). SG

How old are the igneous intrusions in the cave?

None of the intrusions have been dated yet and there are probably a range of ages. It is possible that some intruded into the marble when it was still forming/young and were metamorphosed with the marble. These could be up to 250Ma, but could be difficult to date due to metamorphism. Some are of intermediate composition and are probably associated with the Greyback pluton, with formed around approximately 160 Ma. SG

Is this still an active cave?

Yes as the term can refer to a cave with an active stream or one with actively growing formations, both of which occur in the Cave. However, formation growth appears to have greatly slowed down in the last century or so.

Was all this under water?

Yes. Oregon Caves, like most medium to large caves, formed by solution underwater and then become decorated after they are drained.

Where is the water table?

The River Styx defines the top of the “water table,” but for much of the Caves history it was nearly as flat as a table.

Where does the River Styx go?

River Styx enters Cave Creek shortly after exiting the Cave. Cave Creek enters Sucker Creek 8 miles downstream.

How hard is this rock?

The calcite (3.5 on the Mohs hardness scale) can be scratched with a penny. Gypsum is about 2 on the Mohs hardness scale. It can be scratched with your fingernail but the crystals formed by the reaction of sulfuric acid with calcite in the Connecting Tunnel produced crystals too small to do this.

How easily will these rocks break?

Stalactites several inches thick can easily be broken with one hand providing they are long enough to give enough leverage. Four inch thick stalagmites can be broken by hitting them with a foot. Calcite is an ionic solid, the weak parts of the crystal structure being held together by the attraction between unlike charges of atoms that lack a complete complement of electron in the outermost orbits and hence are electrically charged. Bending the crystal causes like charges to line up opposite one another. This causes repulsion and the crystal breaks, what we call cleavage.

What is cave breakdown?

Cave breakdown is any rock that naturally falls from walls and ceilings or the cave. Usually this breakdown takes place shortly after the cave passage drains of water. In a water filled passage, the water can support as much as 40% of the weight of the ceiling. When the water drains, slabs of rock from the walls and ceilings can collapse into the passage. A good, clear example of cave breakdown is the large ceiling slabs on the floor of the Ghost Room. These slabs fell long enough ago to have speleothems growing on top..

Does anything ever fall down here? Have there been cave-ins in the cave?

People, on a rare basis. Freezing and thawing causes small pieces of rock to fall in Watson's Grotto. A small piece of rock appears to have fallen during possible rotation of a very large mass of rock in the Last Natural Room. The rotation may have been from a minor earthquake in early 1992 or from cave restoration, or it may be unrelated to either of these events. Rocks have fallen in the past, largely blocking some passages and possibly closing previous entrances that were open from 38,000 to at least 50,000 years ago (based on the ages of a grizzly (>50,000 years) and a jaguar (38,600 years) bone found in the Caves. The only rockfall of any note during historic times took place in 1968, when a large rock fell near Miller’s Chapel overnight.

Do tree roots make the cave more stable or less stable or neither? For example, would the growth of tree roots ever cause cave break down or cave-ins?

Tree root make the area more stable. They grip the soil and rocks keeping them in place. Having tree roots is good. When a tree happens to fall in the woods, the root bundle is still holding onto the rocks. There is a good example on the No Name trail by the lower parking lot.

What are the amounts of carbon dioxide, water vapor and oxygen in the Cave?

Carbon dioxide is a gas (CO2) that makes up .033% by volume of most outside air and is partly responsible for the greenhouse effect. Most air in the cave has about double that level of CO2 and it can be up to five times higher in parts of the cave with low air flow. The amount of carbon dioxide in the outside air has probably increased worldwide by at least 30% to 50% in the last 100 years, probably due largely to fossil fuel burning and forest destruction. Oxygen makes up about 21% by volume of the atmosphere. Since carbon dioxide is a heavier gas than oxygen and nitrogen, and water vapor is a lighter gas, their relative partial pressure percentages will be slightly different than their volumes. The difference in oxygen & water vapor levels between the cave and the outside atmosphere is therefore very slight.

Why are these rocks in the ceiling (in the 110 Exit Room) so flat?

A double set of joints has caused rock fall exposing the flat sides of one set of joints. Joints are natural fractures in rock layers along which little or no movement has occurred.

Are there any fossils in the marble or other wallrock?

The marble has been so recrystallized that there are few if any intact fossils in them.

Some crinoid (flower-like animals with waving tentacle on long stalks) fossils have been seen under the microscope in thin sections of rock from the Exit Tunnel. However this is rock that was faulted in under the marble. Given the usual case in the region of younger rock being thrust under older rock, this is likely much younger rock than the marble and so was likely at a time when Earth had recovered from its greatest extinction at the end of the Permian. Like today, crinoids are mostly confined to deeper waters where they survived the extinction event that killed off their cousins who lived at shallower depths.

What are those bags (gray funnel-looking things) for?

They are canvas collection points for water flow and measurement of water quality.

Why aren't there echoes here?

Fairly smooth walls reflect sound uniformly, producing echoes. High humidities also help transmit the sounds. More complex cave walls cause different reflections that partly cancel each other out. However, the relatively smooth walls of the tunnels are not fifty feet apart and therefore don’t allow enough time for our ears to distinguish between our own sounds and the returning echoes. In keeping with the multi-sensory nature of caves, some of these sounds such as flutes, whistling, drums, and singing were felt rather than heard, were legendary rather than audible. Although we cannot directly hear infrasound, existing emotional states appear to be intensified (Ramsayer 2004). In many cultures, cave areas used in ceremonies may have been chosen based on echoes, infrasound, and/or good audible acoustics.

Are there any earthquakes down here?

None have ever been felt by people inside this Cave although sensitive instruments would pick some up. In 1962, an earthquake centered off the coast near Crescent City was felt at the monument but was not felt in the cave. The same happened with minor earthquakes on the Monument in 1991 and 1992. An earthquake did occur about 15 years ago in California and was heard as a rumble inside a cave in northern California. However, no damage was recorded.

Most earthquake damage occurs in loose sediments that shake like a bowl of jelly. Vibrations bounce back and forth, thus sometimes amplifying one another. The solid rock of the Cave would probably suffer little damage as it would move in rhythm with the earthquake. Also, much earthquake damage comes from surface waves that would not greatly affect the deeper parts of this Cave. However, the association of collapsed layers of flowstone (from liquification of sediment which then flows out from under the flowstone) and broken stalactites suggests that major earthquakes every few hundred years (last one in 1700 AD) do cause speleothem damage.

No earthquakes have been recorded by humans inside the Oregon Caves, though three were felt on the Monument's surface (1963, 1991 & 1992). An earthquake did occur near a cave in northern California in 1975 and in Wind Cave in South Dakota in the 1990s and both were heard inside the those caves as a rumble resembling a distant train. However, earthquakes are rarely heard in caves because the infrasound they mostly produce is below the human hearing threshold. Still, infrasound can affect people. While we can’t hear infrasound directly, one study indicates that hearing infrasound can intensify already existing emotional states and may give the impression that someone is watching you. This may have contributed to the belief in spirits living in caves, a belief that may have begun over 78,000 years ago near when we first became human through the use of symbols. Some minor rockfall and movement of critical slopes can occur. Extensive damage only occurs near epicenters of large quakes, as in Missouri caves near the New Madrid earthquake.

Most earthquake damage occurs in the loose sediments that shake like a bowl of jelly. Vibrations in such material bounce back and forth, amplifying one another. However, the solid rock of the Caves would probably suffer little damage as it would move in rhythm with the earthquake. Also, much earthquake damage comes from surface waves that would not greatly affect the deeper parts of the Caves. However, a very large magnitude earthquake, like the New Madrid Earthquake near the Mississippi River, would probably cause some damage, as it did to a cave near that earthquake. Oregon Caves has no-fault insurance. If anything happens we'll all be covered – with hundreds of feet of rock. But it can be promised that you won’t feel a thing.

How is the air so fresh here?

Temperature and air pressure changes outside of the cave induce air flow through the cave.

Did the Eruption of Mt. Mazama (Crater Lake) Have an Effect on the Oregon Caves?

According to John, a 1 inch thick layer of ash from Mount Mazama was found in nearby lakes, so the area was likely affected. However, we have not identified Mt. Mazama ash in the park or in the caves yet. We do not know if there were any localized climate changes that would have affected the cave or growth of the formations, but we are going to try to look into this. SG

What is the difference between forearc and backarc?

The difference between the forearc and backarc is their location. Both forearc and backarc basins form when tectonic stresses cause tension (or stretching) in the overriding plate in a subduction zone. A forearc basin forms between the subduction trench and the volcanic arc. A backarc basin forms further from the subduction trench, on the other side of the volcanic arc. A good example of a backarc basin is the sea separating Japan (the volcanic arc) and China (the rest of the continental plate). Both can have associated volcanism, faulting, sedimentation, etc. SG

Why isn't there more color down here?

Lint from people's clothing, smoke from torches, candles and carbide lamps, skin oils from touching and skin flakes have dulled some colors on ground formations near the paved trails. Bright colors in caves are almost exclusively due to colored lights, which we have chosen not to use except for the UV light and eventually some yellowish lights to reduce the human-caused growth of algae and bacteria.

Is there anything valuable down here? Have gold or precious minerals been found in the Cave?

Only that which is beautiful, rare, mysterious, and full of wonder. Precious metals are usually associated with formerly molten rock or stream deposits. By contrast, most of the cave rock formed as a chemical precipitate. However, the Exit Tunnel does pass through faulted and metamorphosed mudstones where hot water solutions apparently brought in and deposited iron pyrite (fool's gold), which often is associated with small amounts of gold. But consider this: What is it about gold that has caused us to destroy beautiful natural areas and wipe out entire cultures to obtain it? It only became a valuable commodity about 6,000 years ago.

CAVE GEOMETRY

How do they measure depths and heights in the cave?

Most passages in park caves have been surveyed with a compass and tape measure. Parts of the main trail have been measured with surveying instruments (rod and transit). GPS units don’t work underground so some permanent tags have been put in to the relocated sampling locations, etc.

Are there instruments that can measure depth (to find isolated cave pockets, etc.)

Yes. Measuring electrical resistance, evaluating reflections from solar radiation or man-induced shock waves and using ground penetrating radar are methods to determine what is in the subsurface. If there is a cave in between two measured points, the electrical resistance will increase. Evaluating shock waves can differentiate between a few percent change in the amount of pore space. Using reflections from solar radiation is not as accurate. None of these methods can tell us whether there is a pore in the rock big enough for a person to get through (ie, a cave).

Does this cave go any deeper than what we see?

Perhaps a small amount down to the base of the marble block, but that area would be filled with water.

How deep are we?

In absolute elevation, the lowest part of the cave trail is at the entrance. The approximate distances in feet below the surface are:

WATSON'S GROTTO - 65

PETRIFIED GARDENS – 55

BRIDGE OVER RIVER STYX - 60

PASSAGEWAY OF THE WHALE - 50

CONNECTING TUNNEL - 85

DRY ROOM - 65

IMAGINATION ROOM - 35

BEEHIVE ROOM - 35

110 EXIT - 30

BANANA GROVE – 35

NIAGARA FALLS - 85

NEPTUNE'S GROTTO - 55

GRAND COLUMN - 135

WIND TUNNEL - 155

MILLER'S CHAPEL - 165

RIMSTONE ROOM - 195

GHOST ROOM - 200

PARADISE LOST - 190

ANGEL FALLS - 170

EXIT TUNNEL – 135

Is Oregon Caves the largest marble cave?

Oregon Caves is the largest marble cave system west of the Rockies. However, it should be noted that it is difficult to find the sizes of other cave systems to accurately compare Oregon Caves to other caves.

BIOLOGY

What kinds of animals live in the cave?

Depending on the time of year, the most visible ones are harvestmen, fungus gnats, crickets, millipedes, moths, ants, and bats. Springtails are quite common but you have to look closely to seen them.

Are there any poisonous animals in the Cave?

No, except for some small spiders and centipedes which are not known to bother humans. Their fangs or stingers are generally too small to penetrate human skin. The hobo spider usually hangs out in the cedar bark siding of the historic building and has never been found in the caves.

Do fish live in the River Styx? Are there any (blind) fish in the stream?

None have been found. Water from our outside stream is filtered through sediment and has only a short run on the surface before it enters the cave so it can’t bring in enough organic debris (leaves, twigs, etc.) to support fish.

Many US cave fish derived from the flooding of a large part of the Mississippi Basin by the Gulf of Mexico. Cave fish evolved from marine fish that were stranded there over fifty million years ago as waters receded. However, we are on the leading side of USS North America (an active tectonic plate margin), a setting which lacks the broad, flat coastal plain and continental shelf where changes in sea level could trap fish in karst environments, thereby allowing them to evolve into ‘cave fish.’ It is also a place where limestone is much less likely to form due to the high level of geologic/tectonic activity. Therefore extinction rates are likely relatively high.

Is this root dead (Bridge Over River Styx)? When did it die?

The root is a Douglas fir root. During hazard fuel and wood-falling-on-the-buildings reduction behind the Chalet, the tree was cut down in 1962.

What bats and/or how many are there in the Cave?

Five of eight population size estimates in 1988 ranged from 785 to 873 (Cross, 1989) during late summer and early fall swarming. A 2002 study indicated that similar numbers are in the Cave but bats will have to be counted at the main entrance and Carbide Entrance to be sure as the bats seem to be using the 110 Exit and maybe other entrances (other than the Exit) more in the last decade. Bats visible from the main trail in winter usually do not number more than a few dozen. Eight species have been found in the cave, the most numerous being the Western Long-Eared bat, but the Yuma Myotis and the Townsend’s Big-Eared bat are those most commonly seen along the tour route.

Is there bat guano in the Cave?

There is very little guano in the cave. Our bats spend most of their time in the forest and tend to defecate there rather than in the cave.

Are there blind salamanders here?

No. There are only a few types of blind cave salamanders known in the world and they usually evolved in much larger limestone systems. Oregon Caves is part of an isolated block of marble and it is unlikely that a blind cave salamander will migrate from a large limestone area. Also, the lack of blind cave salamanders in the West results from the fact that most western caves occur in mountainous areas and simply are created and destroyed too quickly for new species of vertebrates to evolve. With so few refuges from flooding, drought, etc., extinction rates may be high as well. Insects tend to evolve faster since they have a faster turnover of generations than do most vertebrates; hence the relatively large number of endemic invertebrates here.

Do the wood rats in the caves carry hantavirus?

According to the hantavirus information from the CDC and confirmed with John Roth, hantaviruses have never been found in wood rats. It has been found in deer mice, white-footed mice, rice rats, and cotton rats. Hantaviruses are also extremely rare west of the Rockies with only one case occurring in Yosemite National Park. In addition, the viruses require dry conditions and therefore do not thrive in the damp cave environment. Hantavirus has been found in the guide shack at Oregon Caves National Monument, but it was found in the mice droppings, not the wood rat droppings. Therefore, there is little to no risk of transmission of hantavirus from wood rat feces in the cave.

Why are the trees dying at the cave exit?

Most are dying of old age, increased competition for water due to the increased tree density as a result of fire suppression, and a longer dry season (snow packs on the average half the thickness of previous decades). Tree mortality in the West has doubled in the last few decades, mostly likely as a result of warming. Parasites called dwarf mistletoe may accelerate this mortality by withdrawing more water and nutrients from trees already under stress from old age (their conducting vessels get plugged up, similar to arteriosclerosis in humans). Increased tree density likely also increases the spread of dwarf mistletoe. The majority of the dead trees are Doug-firs which usually need fire for their seedlings to grow as they are intolerant of shade. The lack of fires in the last 100 years or so has greatly reduced their reproduction, and favored the current dense stands of true firs and cedars which are shade-tolerant.

What is that tree with the peeling bark?

Pacific Madrone (Arbutus menziesii). Some green bark is exposed when the outer bark peels, but whether the tree benefits from this increased photosynthesis is unknown. Not all features in a species are adaptations for survival.

What kind of bark is on the outside of the lodge?

The Port Orford cedar bark siding was taken from a railroad tie cutting operation up Grayback Creek from Grayback Camp, near the modern Grayback campground. The Port Orford cedar is considered a paleoendemic or relict, meaning that its range (based on fossils) was once more extensive and the tree is now largely confined to the Klamath-Siskiyou bioregion. The tree is fast becoming extinct as a commercial tree as logging trucks, streams, rivers, and even boots of hikers spread a mold of the genus Phytophthora which attacks the cedars. Other species in the same genus cause sudden oak death syndrome & the potato blight, and attack many more trees than these species.

What mosses live on the trees here?

Epiphytes, mostly various species of the genus Orthotrichum and Isothecium. There is no common name for these mosses. What visitors refer to as “moss” are actually lichens, especially Bryoria and Usnea. Any plant that grows on another plant and is not parasitic is called an epiphyte.

What happened to the fish that were in the pond?

The biggest ones were removed secretly by an unknown fisherman at night and was apparently undetected by hotel guests and staff. The rest were removed publicly by the Park Service because of concerns with them being non-native fish, and the possibility that they could have introduced diseases such as whirling disease. Also, at various times in the past concessionaire staff apparently made meals of some of the fish.

Is bone made of calcite?

No, bone is made out of a combination of apatite (calcium hydroxyl phosphate) crystals and collagen fibers. Collage is a protein. However, eggshells such as those of a chicken are made of calcite and protein.

HUMAN HISTORY

Who discovered this cave?

The first record of cave entry was by Elijah Davidson in the fall of 1874 while hunting a deer. According to Davidson's own account, he entered the cave to rescue his hunting dog Bruno, who had chased a growling animal into the cave and was howling as if in pain. It is unknown how far he went into the cave. When he emerged he baited the entrance of the cave with the deer he had shot, and killed the bear when he and his brother-in-law Jules Goodwin returned to the cave the next day. And yes, Bruno made it out of the cave as well. No, we don’t know what kind of dog Bruno was, but Davidson generally preferred Airedales for hunting.

Did the Indians ever find & enter the Cave?

There is no definite evidence that Native Americans ever entered the Cave. Only one arrowhead has been found on the surface within this national monument. However, it is likely that they did find the cave at some time.

Why is it called Oregon “Caves” instead of Oregon “Cave?”

The term “Oregon Caves” was first used by the San Francisco Examiner newspaper likely as a way to differentiate between those in Oregon and those in northern California. Also, most likely the first entrances discovered were the current Main Entrance and the nearby Carbide Entrance. The 110 was likely discovered in 1877 and was believed for a while to be a different cave, hence the name “Caves.” They were later found to be the same cave. There are other caves within the monument boundaries, but they are very small and relatively inaccessible.

What is the difference between a National Park and a National Monument?

National Parks are created by an act of Congress. National Monuments are proclaimed by the President.

When was the hotel built?

Construction began in 1931and the six-story Chateau was completed in 1934 at a total cost of $50,000. The Oregon Caves company sold stocks to finance it.

The timber for the Lodge (Chateau) was cut from an island in the middle of Sucker Creek by the Baldwin Ranch near the modern Grayback Campground, and hauled to the mill by truck. The Villair and Anderson Mill on Caves Highway at Milepost 14 milled the lumber. Madrone (Arbutus) balusters support a fir handrail. The ballroom is maple floored and the fireplace on the fourth floor (lobby) is made of marble rocks blasted during construction. A stream runs through the third floor dining room and is crossed by two bridges. A sprinkler system was installed on the roof of the Lodge. The building is 60 by 120 and 104 feet high and is steam heated.

The Oregon Caves Chateau opened on May 12 after it received two large loads of “Monterey” furniture, much of it made especially for the building. It has a redwood shake roof, with eaves supported by cedar cornice brackets. Inside, there is a 36’x60’ maple dance floor and a double fireplace 14 feet across. The 5673 square foot building contains 26 bedrooms, 22 of them for visitors. The paneling is "Nu-Wood", a product that was made in Kloquet, Minnesota.

When were the first pathways and lights put in?

The first iron ladders were constructed in the cave in 1921. The first electrical lights were installed in 1930. The first entrance gates were installed in the 1950s. Nearly all of these (except the Paradise Lost stair base, which was replaced in the sixties, and the Exit Gate) were replaced during cave restoration from 1992 to 2004.

What are the black arrows for?

They were put on cave walls for early explorers to find their way out. Most if not all are made by the soot from carbide lamps.

Are there any plans to extend the trail?

No. The present trail length is more than adequate for most people. Entry to the rest of the cave would entail considerable construction damage. This relates to the small size of the cave. Visitors can already see about 1/4 of the volume of the known cave from the trail. However, caving tours off the paved trail are now given by ranger sin summer.

What is the average grade of the Exit Tunnel?

16%

How many people visit Oregon Caves each year?

Approximately 75,000 people per year visit the monument and about 60,000 will tour the cave. Over 4 million people have seen the cave.

How many of you work in the park?

The NPS staff varies from about 8 to 40, depending on the season. The concessionaire has a maximum of about 40 employees when the Chateau is open (usually May – October).

Do you ever close the cave or park?

The cave is closed from early December until mid-March to accommodate bat hibernation. Parts of the trail are closed when tours start if enough bats are present by the trial. The park may be closed due to icy or very snowy conditions on the access road, but otherwise remains open all year.

Did anybody die down here?

Frank Ellis accidentally fatally shot himself in the head with his own revolver in 1909.

Why don't you use colored lights? How many lights are there?

The Park Service protects natural systems and processes and is not mandated to make the natural scenery "prettier." Colored lights would confuse people as to what were the actual colors of the cave rock. There are about 212 lights in the cave.

Can you drink the water from the cave?

Humans and other animals have added organic material to pools, especially those pools near the paved trail. The result may be potentially dangerous bacteria in the pools. Even areas that have not been visited by people may not have been completely pure water since the rock in which this cave formed is too porous to filter out all of the bacteria and viruses that may come in from the earth's surface, such as someone defecating on the Cliff Nature Trail.

Do you have power failures?

There are about one or two power failures a year.

Where do you get your power?

Pacific Power which gets most of its power from hydroelectric.