C: Geology = the Changing Earth 1.4 Getting a Handle on Time Flashcards
Who was William Smith and what was his significance?
William Smith (1769-1839) was a geologist known for mapping sedimentary rock layers in England.
What are catastrophist theories?
Catastrophist theories are explanations that attribute past changes in the Earth to violent events such as earthquakes, volcanic eruptions, and floods.
What did William Smith propose about sedimentary rock layers?
Smith proposed that the sedimentary rock layers he mapped were deposited by a series of catastrophic floods.
What types of events are considered in catastrophist theories?
Events such as earthquakes, volcanic eruptions, enormous floods, meteorite impacts, and upheavals of Earth’s crust.
In what centuries were catastrophist theories particularly influential?
The eighteenth and nineteenth centuries.
Fill in the blank: Catastrophist theories involve processes of a different type or intensity than those observed in the _______.
present.
True or False: Catastrophist theories suggest that past geological changes were gradual and uniform.
False.
What is uniformitarianism?
The principle that the geological processes in action today have always fundamentally operated in the same way throughout Earth’s history
This concept is often summarized by the phrase ‘the present is the key to the past.’
Define unconformity.
A surface in a rock sequence that represents a break in the pattern due to erosion or a lack of deposition
Unconformities can indicate significant geological time gaps.
What is uniformitarianism?
The principle that the geological processes in action today have always fundamentally operated in the same way throughout Earth’s history
This concept is often summarized by the phrase ‘the present is the key to the past.’
Define unconformity.
A surface in a rock sequence that represents a break in the pattern due to erosion or a lack of deposition
Unconformities can indicate significant geological time gaps.
What is sedimentary rock composed of?
Eroded fragments of other rock
Sedimentary rock forms from the accumulation and compression of these fragments.
How are sedimentary rocks formed?
From layers of sediment under relatively low temperatures
Sedimentary rocks form at the surface of Earth.
What is the origin of igneous rock?
Formed when molten magma intrudes into the crust or extrudes onto the surface
Igneous rock can form from magma that cools either underground or above ground.
What conditions lead to the formation of metamorphic rock?
Intense pressure and heat
Metamorphic rock is formed from sedimentary or igneous rock transformed at the molecular level.
Where are igneous rocks typically formed?
Deep within Earth’s crust and mantle under extreme heat
The entire mantle is composed of igneous rock.
What geological processes are associated with the formation of metamorphic rocks?
Collisions between crustal plates
Metamorphic rocks can form at tectonic plate boundaries where pressure and heat are significant.
What is the process called that describes the continual change of rocks from one type to another?
rock cycle
The rock cycle includes various processes such as weathering, erosion, and deposition.
What are the three main types of rocks involved in the rock cycle?
- igneous rocks
- sedimentary rocks
- metamorphic rocks
Each rock type undergoes transformation through various geological processes.
According to Hutton, where do all rocks start their formation?
molten magma within Earth’s mantle
This magma cools and solidifies to form igneous rocks.
What happens to igneous rocks after they form?
They weather and erode
Weathering and erosion are caused by elements such as water and wind.
Fill in the blank: The process by which sediments are laid down is called _______.
deposition
Deposition is a key process in forming sedimentary rocks.
What are sediments typically formed from?
weathered and eroded rock materials
Sediments can also include organic materials and minerals.