54 terms

Unit 7: Test Review

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What is the Principle of Original Horizontality?
sediments are originally deposited horizontally under the effect of gravity
What is the Principle of Superposition?
a principle holding that the youngest layer on top and the oldest on the bottom
What is the Law of Cross-Cutting Relationships?
Whatever is crossing over a set of rocks is younger than that set of rocks.
What is the Principle of Lateral Continuity?
Sedimentary rocks are laterally continuous over large areas.
What is a syncline and what is the relative age of the rocks in the middle?
smiley face; a fold of rock layers that slope upward on both sides of a common low point. - youngest layer in middle; oldest layer away from middle.
What is an anticline and what is the relative age of the rocks in the middle?
frowny face; a formation of stratified rock raised up, by folding into a broad arch so the layers slope down on both sides from a common crest - oldest IN the middle.
Describe an unconformity.
An unconformity is an erosional surface between two rock units or layers.
Disconformity
an erosional surface between 2 sedimentary layers that are parallel to each other - hard to spot in the field.
Angular Unconformity
an erosional surface between 2 sedimentary layers that are NOT parallel to each other (thus, they are at an angle to each other)
Nonconformity
an erosional surface over NON-sedimentary rock with sedimentary rock on top of it.
What is a Fault?
A fault is the breaking of rock - earthquakes occur along fault lines. This is an example of a cross-cutting relationship.
In an undisturbed rock column the layers on the bottom will be the oldest and the youngest rocks will be on the top. What is this called?
The Law of superposition
layers of sediment are originally deposited horizontally under the action of gravity. What is this called?
The principle of original horizontality
Sedimentary rocks are laterally continuous over large areas. What is this called?
The Law of Lateral continuity
A principle holding that an igneous intrusion or fault must be younger than the rocks it intrudes or cuts across. What is this called?
The Law of Cross Cutting Relationships
An example of a structure that cross-cuts a geologic column.
Structural relationships may be faults or fractures cutting through an older rock.
An example of a structure that cross-cuts a geologic column.
Intrusional relationships occur when an igneous magma is intruded into pre-existing rocks.
An example of a structure that cross-cuts a geologic column.
Stratigraphic relationships may be an erosional surface (or unconformity) cuts across older rock layers, geological structures, or other geological features.
Uniformitarianism
The geological processes that took place in the past are generally similar to those that occur now.
What does Conglomerate sedimentary rock tell you about the original environment?
Conglomerate sedimentary rock is composed of rounded gravel, pebbles, cobbles, or boulders along with smaller rock pieces and shows an extremely high energy of transport like a fast moving river or a glacier.
What does Sandstone tell you about the original environment?
Sandstone is composed of sand and indicates moderate energy of transport. form a beach or a desert.
What does Shale tell you about the original environment?
Shale is composed of clay sized particles and indicates a low energy of transport like a calm marine/ocean or muddy environment.
What does Limestone tell you about the original environment?
Limestone is a sedimentary rock rich in calcite made for the shells of marine animals. Limestone forms in quiet shallow ocean water beyond the beach (sandstone) and beyond the near shore (shale) environments.
What does Extrusive Igneous rock tell you about the original environment?
Extrusive Igneous Rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava and may also be found intruding into older rock formations.
What do Igneous rocks and regional metamorphic rocks tell you about the original environment.
These rocks form deep underground and are exposed on the surface only after extensive uplift and erosion. These may be granite, gabbro, gneiss or schist.
Describe an angular unconformity - be able to recognize a diagram like on Review #9.
Angular unconformities must have rocks below the unconformity line that are tilted.
Describe a disconformity - be able to recognize a diagram like on Review #9.
Disconformity is an unconformity that has erosion between two layers of sediment. There might even be a layer missing
Describe a paraconformity - be able to recognize a diagram like on Review #9.
Paraconformity is an unconformity that has little or no evidence of erosion because the layers are parallel and some are missing.
Describe a nonconformity - be able to recognize a diagram like on Review #9.
Nonconformity is an unconformity where igneous or metamorphic rock is exposed and weathered, then sedimentary rock builds above it.
When interpreting a rock column, what type of rock would you need to see to assume that there was once a marine or ocean environment?
Sandstone - beach
Shale - shallow sea
Limestone - ocean
When interpreting a rock column, what type of rock(s) would have no fossils at all
Igneous and metamorphic rocks would have no fossils at all -
If a fault cuts through some layers of rock and the top layer on one side is thicker than the same rock layer on the other side, why is this?
The thinner layer has been exposed to more erosion than the other side.
What kind of energy is associated with conglomerate rock?
High energy either form a fast moving river or a glacier.
What kind of energy is associated with shale rock?
Low energy is associated with shale as it indicates a shallow sea or muddy environment.
What kind of energy is associated with sandstone rock?
Mid energy is associated with sandstone rock from slower moving water, beach, or windy desert.
What kind of energy is associated with limestone rock?
Low energy is associated with limestone rock as it indicates an ocean or marine environment.
How is a dome formed?
Rock is uplifted and then partially eroded. Older rock in the middle.
How is a basin formed?
Rock is uplifted away from a point and forms a basin. Younger rock is in the middle.
If you have two rock layers made of that same type rock, what could you look for to tell if one was older than the other?
They type of fossils in each would determine the age of the rocks. Remember that index fossils can tell absolute age.
If you see a wavy line on a geologic cross section, what does it mean?
It means that there is an unconformity there.
If you see a line with triangles attached to it like teeth, what does it mean?
It means there is a fault there.
Look at diagram on review #10 and be able to put the rocks in the correct order.
Oldest: A, B and N, C, D and M, E and L, F and K, J, I, G, H is youngest.
Look at diagram on the left side of review #11 and be able to indicate the age of the intrusion.
The intrusion is the youngest since it cuts through every layer of rock.
Look at diagram on the right side of review #11 and be able to indicate the relative age of the unconformity and tell what kind of unconformity it is.
The unconformity is older than layer B but younger than layer C. It is an angular unconformity.
What type of fossils might you find in the Paleozoic era age rock?
early fish, trilobites
What type of fossils might you find in the Mesozoic era age rock?
Dinosaurs, early birds, reptiles, early small mammals, ammonites
What type of fossils might you find in the Cenozoic era age rock?
large mammals, early man
If you find trilobite and fish fossils in the same rock layer, what might you think was the environment that the sediment that made the rock was formed in?
Ocean or marine environment.
If you find a dinosaur bone, or mammal fossil, what might you think was the environment that the sediment that made the rock was formed in?
Land or swampy environment
What was the predominant life forms of the Paleozoic era?
Fish, trilobites
What was the predominant life forms of the Mesozoic era?
Reptiles, particularly dinosaurs
What was the predominant life form of the Cenozoic era?
Age of mammals
If you were looking for evidence of caves, what type of rock would you look for?
Caves are formed only in sedimentary rocks.
If you see metamorphic rock on the surface of the earth, what does that tell you about that rock?
Metamorphic rock is formed deep within the Earth's crust and must have been uplifted to get to the surface.
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