Module 6: Foundations of Geology Flashcards
Define: Uniformitarianism
The view that most of the earth’s geological features are the result of slow, gradual processes that have been at work for millions or even billions of years
Define: Catastrophism
The view that most of the earth’s geological features are the result of large-scale catastrophes such as floods, volcanic eruptions, etc.
Define: Humus
The decayed remains of once living creatures
Define: Minerals
Inorganic crystalline substances found naturally in the earth
Define: Weathering
The process by which rocks are broken down to form sediments
Define: Erosion
The process by which rock and soil are broken down and transported away
Define: Unconformity
A surface of erosion that separates one layer of rock from another
Which hypothesis (uniformitarianism or catastrophism) requires that the earth to be billions of years old?
The uniformitarian hypothesis.
The uniformitarian hypothesis requires that the earth be billions of years old, because it assumes the geological features of the earth took millions and billions of years to form. Catastrophism is more flexible. It can accommodate a young earth or an earth that is billions of years old.
What are the three basic types of rock?
The three basic types of rock are: igneous, metamorphic, and sedimentary.
What agent is responsible for laying down most of the sedimentary rock we see today?
Most sedimentary rock has been laid down by water.
How is each type of rock (igneous, metamorphic, sedimentary) formed?
Igneous rock is the result of molten rock that cools and solidifies. Sedimentary rock is formed when sediments fuse together. Metamorphic rock is formed when either sedimentary or igneous rocks change, usually as a result of temperature or pressure.
A rock in the desert is constantly bombarded by bits of sand that are carried on the wind. Sometimes the sand hits the rock so hard that tiny chips of the rock or broken off. As time goes on, the constant beating of the sand on the rock wears the rock down, and it gets much smaller. Has the rock experienced physical or chemical weathering?
This is physical weathering.
The small chips of rock that are broken off are just miniature versions of the original rock. No change in composition has occurred.
When limestone is exposed to weakly acidic water, it breaks down, forming a gas in the process. Is this chemical or physical weathering?
This is chemical weathering.
The limestone forms of gas. That changes the composition of what’s left.
A geologist is comparing the erosion that occurs as a result of two different rivers. The first river flows quickly while the second flows slowly. Which river do you expect to cause the most erosion?
You expect the most erosion from the quickly flowing river.
Remember, the faster the water moves, the more erosion that occurs.
Two hillsides in the same community experience a very heavy rain. The first hillside is covered with grass and flowers, while the second is mostly bare. Which hillside will experience the most erosion?
The bare in Hillside will experience the most erosion.
Remember, that plants reduce the effects of erosion.
What causes a river to form a delta?
A river’s delta is formed because the river deposits many of the sediments it carries there.
What kind of water is responsible for eroding underground caverns?
Underground caverns are eroded by groundwater.
What is the difference between a stalactite and a stalagmite?
Stalactites form on the ceiling of a cavern, while stalagmites form on the floor of a cavern.
(I remember this by thinking about how tightly something has to be attached to a ceiling to keep from falling. Stalagmites can get large and heavy and have to stand upright with all their might. :)
What causes stalactites and stalagmites to form?
Stalactites and stalagmites are formed when groundwater seeps through the ceiling of the cavern. As the drop forms and falls to the floor of the cavern, it might deposit sediments on the ceiling or the floor. As those sediments pile up, stalactites and stalagmites are formed.
If an unconformity exists between two parallel strata of sedimentary rock, what kind of unconformity is it?
It is a disconformity.
