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18 Cards in this Set
- Front
- Back
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columnar jointing
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polygonal in cross section, form by contraction as a lava flow cools
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fumarole
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steam vents that puff in both the upper and lower basins. Some become spouters of small geysers if the water table is high enough
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travertine
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dense, massive or concretionary limestone formed by rapid chemical precipitation of calcium carbonate.
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Like Hawaii,Yellowstone sits on top of a hotspot.Cite and briefly explain two lines of evidence for this, other than the presence of hydrothermal (hot water) features such as hot springs, geysers, and mud pots.
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A thick continental crust overlies the Yellowstone hot spot. The hot spot has remained stationary and the centers of volcanic activity have shifted. In general, the ages of the volcanic rocks tend to fit this model. Major eruptions have been more episodic.
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What is a geyser?
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A geyser is an intermittent hot spring that regularly or irregularly erupts jets of hot water and steam, as a result of ground water being heated by hot rock, creating steam under conditions preventing free circulation.
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What three basic conditions are necessary for the development and ongoing eruptions of a geyser?
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A powerful heat source, plentiful supply of water and watertight plumage system
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Explain the processes involved in the eruption of a geyser.
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Water boiling in the geyser system produces steam bubbles, causing expansion and overflow at the surface. With pressure suddenly reduced, water trapped in side chambers flashes into “steam.” The resulting “explosion” clears the upper part of the geyser tubes and shoots water and steam into the air. An eruption happens when enough water seeps into the system and becomes superheated, filling all tubes and side chambers.
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What is the role of siliceous sinter in a geyser’s underground “plumbing”?
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Sinter is a chemical sedimentary rock that is very siliceous, that is deposited as a hard encrustation in the geyse’s underground system. The sinter deposits help keep the system nearly watertight and tend to produce constrictions that prevent free circulation of water.
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Why do ordinary, continuously flowing hotsprings not erupt?
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Hot springs don’t erupt because where boiling water is not constricted, it rises through the tubes and flows out continuously.
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Absaroka volcanics
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large range, trending northwest-southeast, 10,000-12,000 feet high, have been intensely eroded by streams and glaciers and form a jumble of steep ridges above fairly broad valleys. Made up of over 10,000 feet of mainly andesitic, pyroclastic volanics. The tuffs, breccias, and lavas of the supergroup overlie older metamorphic and sedimentary rock sequences.
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Mammoth Hot Springs
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a mountain of travertine terraces covering nearly a square mile (travertine is a dense, massive limestone formed by rapid chemical precipitation of calcium carbonate). The buildup of travertine deposits by precipitation is rapid. Thick beds of marine limestone underline Mammoth Hot Springs. Presently it is the largest carbonate-depositing spring system in the world.
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Upper Geyser Basin
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Upper basin has the highest concentration of geysers and hot springs.
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About how many ancient forests are preserved at Specimen Ridge in Yellowstone National Park?
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20 or more successive forests (the exact number is uncertain)
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What events killed the trees?
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Violent eruptions from the Absaroka volcanic field
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What is the mode of preservation of the fossil trees?
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Root systems of some were preserved. The trees were lithified as silica-enriched ground water infiltrated and preserved the woody structure
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What is their orientation?
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Tree trunks stick up through volcanic material in lifelike positions. Erosion of volcanic material on the slopes has reserved these fossil forests that were buried along time ago by Eocone ash flows and lahars (mudflows).
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How old are they (state an epoch from the geologic time scale)?
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Eocene
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What was the climate like at that time, and how can we tell?
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Eocene climate throughout this time remained mild and humid
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