Cave popcorn can be pale white like popcorn waiting for all the fixings or a deep yellow, reminiscent of the butter-soaked mounds behind the glass at a movie theater concession stand. Refills, please! That crunch you hear from pressing the crust of freshly baked bread? To geoscientists, a bomb is a rock that is over 64 millimeters about 2 inches in diameter that forms when molten lava is hurled from a volcano.
If the outside has hardened but the inside is still soft, gases trapped in the rock can expand and crack the outer skin like a rising bread loaf. The impact of the bomb hitting the ground can also crack the hard shell. These cracks can leave a pattern that sometimes looks like the cracked crust of bread, earning these rocks their name. A fun note: Volcanic bombs that get flattened during their landing are sometimes called pancake bombs. Also called flowstone, cave bacon forms when water smoothly runs down an overhanging wall over and over.
The mineral buildups produce a long, thin sheet, with undulations similar to crisp slices of bacon. Variations in the chemicals in the slowly dripping cave water even create colored stripes akin to alternating bands of fat and meat.
Care for some moist, springy yellow cake with a thick coating of chocolate for dessert? Yellowcake , without that very crucial space between the words, is the powder form of uranium oxide. It is made when preparing fuel for nuclear reactors from mined uranium. Like any good cake, there are a couple of ways to cook it up. You can mechanically grind the uranium ore and dissolve the uranium oxides with acid.
Or you can skip the mining and dissolve the uranium into groundwater with a high oxygen content, which can then be pumped to the surface.
However, the color of yellowcake depends on the drying temperature and can even be dark green. It is hard Martian rock. Stalagmites are convex floor deposits built up by water dripping from an overhead stalactite or from the cave ceiling.
Because falling water droplets tend to splash, stalagmites spread out as they gradually build up from the floor. Hence, they do not have central, hollow tubes like stalactites. Stalagmites are usually larger in diameter than the stalactites above them and they generally have rounded tops instead of pointed tips. When a drop of water falls from the ceiling or stalactite, it still has some material left in solution. When the drop hits the floor, carbon dioxide is given off and carbonate material is precipitated as a mound below the point of dripping; or, if a noncarbonate mineral, evaporation causes precipitation of mineral material.
Stalagmites can assume a fascinating variety of shapes and people have compared them to broomsticks, totem poles, toadstools, bathtubs, Christmas trees, beehives, coins and buttons, and even fried eggs! Columns are not stalactites nor are they stalagmites; they are both, together. When a stalagmite grows together with its counterpart feeder stalactite, a new speleothem is formed: a column or pillar. Columns can reach gigantic proportions, sometimes over 65 feet 20 m in height and diameter. Typically the largest columns are aligned along ceiling joints, where the greatest amount of water is dripping into the cave.
Flowstone is one of the most common speleothems. Where composed of calcite, individual flowstone layers may be very colorful: yellows, reds, and oranges. Flowstone differs from coatings in that it deposits from flowing water and not from seeping water, but in reality, these two speleothem types are intergraded Hill, Flowstone forms both in the open air and under water and assumes a variety of forms.
The most common of these is the petrified or frozen waterfall, also referred to as cascades, rivers, glaciers, or organ pipes. A well know example of waterfall flowstone is Frozen Niagara in Mammoth Cave.
In places, flowstone can form on sedimentary rock, which is later washed away, leaving the flowstone as a canopy. Flowstone also forms in running streams where carbon dioxide degasses as water tumbles over rocks in a stream bed. When water drops flow down a sloped ceiling before dripping to the floor, calcite can build up in a line.
Iron oxide or organic solutions form the baconlike stripes. As the formations grow, small undulations in the bedrock cause the draperies to become slightly curved. With time these curves become more and more accentuated so that the draperies become highly folded or furled along their lower edges. Dripstones may form at the bottom of draperies where the furls are steep enough for water droplets to fall to the floor.
Caves are greenhouses for flowers formed of cave minerals, typically gypsum. The crystal petals of these speleothems radiate out from a common center. The formation grows from a base rather than a tip like stalactites.
Variations in crystal structure produce unique, curved, flowerlike petals. Cave flowers have been found in may caves throughout the world. Hovey Hovey, must have been quite taken by the gypsum flowers when he saw them in Mammoth Cave in for he describes them in overtly flowery language:. From a central stem gracefully curl countless crystals, fibrous and pellucid; each tiny crystal is itself a study; each fascicle of curved prisms is wonderful; and the whole blossom is a miracle of beauty….
Floral clusters, bouquets, wreaths, garlands, embellish nearly every foot of the ceiling and walls…. Clumps of lilies, pale pansies, blanched tulips, drooping fuchsias, sprays of asters, spikes of tube-roses, wax-leaved magnolias—but why exhaust the botanical catalogue?
The fancy finds every gem of the green-house and parterre in this crystalline conservatory. Frostwork is a needlelike speleothem resembling cactus or thistle plants. It is the acicular habit of aragonite that gives most frostwork its spiny appearance.
However, frostwork can be composed of calcite, opal, gypsum, other minerals, and ice. It is usually white but can also be other colors, including blue Hill, The most common occurrence of frostwork is with coralloids, for example, clusters of needles frequently radiate from the tips of popcorn nodules.
Frostwork can also be found on stalactites, walls, ceilings, ledges, and less occasionally on floors Hill, Frostwork displays can be dazzling! They are among the most exquisite, fragile, and intricate of all speleothem types. Unfortunately, their beauty makes them prime targets for vandalism, and their delicate nature makes them easily destroyed by carelessness. Questions, Comments, Concerns, Quandaries.
Down the Rabbit Hole. About PHS. Homework Classwork Tutoring. Science in the Media.
0コメント