Transcript Getting a Handle on Time

Getting a Handle on Time
C1.4
Forces of Catastrophe
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During the 18th and 19th centuries geologists considered
violent events such as earthquakes, volcanoes, floods, etc
to be the main mechanisms of past change.
William Smith proposed that he sedimentary rock layers
he mapped were deposited over England by a series of
floods.
These violent explanations are now called catastrophist
theories.
A main component of these theories is that they involve
processes of a different type or intensity that than those
observed in the present.
How Much Time?
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These early theories of catastrophism fit in well with
human experience.
The processes at work in the present seem too weak and
slow to explain evidence of a dramatic change in Earth’s
past.
It’s hard to imagine that the slow processes observed in
the present could have resulted in the badlands, Mount
Rundle, or Red Rock Coulee.
Complex Histories
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James Hutton believed that to unlock the mysteries of the past, you
must understand the processes at work in the present.
This was is the principle of uniformitarianism
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The principle that the geological processes in action today have always
fundamentally operated in the same way throughout Earth’s history.
Hutton observed nearly vertical layers of rock beneath horizontal
layers.
This lead him to first propose that the bottom layers were originally
deposited horizontally but were subsequently tilted.
Then, after a long period of erosion, many layers were deposited
horizontally on top.
This is called an unconformity
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A surface in a rock sequence that represents a break in the pattern due
to erosion or a lack of deposition
What are Minerals & Rocks?
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Minerals: A mineral is a pure natural substance
(element or compound)
Rocks:is a natural substance that contains one or more
minerals held together. The 3 types of rocks that cycle
are:
1.
2.
3.
Igneous
Sedimentary
Metamorphic
What Are Igneous Rocks?
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Igneous rocks are formed when
magma from Earth's core rises,
cools, and solidifies forming
crystals (called crystallization).
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Magma that moves out of the crust
and cools quickly is called extrusive
igneous rock (pumice). These
igneous rock have small crystals.
Magma that never reaches the surface
and cools slowly is called intrusive
igneous rock (obsidian). These
igneous rock have large crystals.
What Are Sedimentary Rocks
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Sedimentary rocks are made
up of sediments eroded or
weathered from igneous,
metamorphic, other
sedimentary rocks, and even
the remains of dead plants and
animals. These materials are
deposited in layers, or strata,
and then are squeezed and
compressed into rock (called
lithification).
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Most fossils are found in
sedimentary rocks.
What Are Metamorphic Rocks?
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Metamorphic rocks are produced
when sedimentary or igneous rocks
are transformed by heat and/or
pressure.
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The word "metamorphic" comes
from the Greek language, which
means "to change form."
What is The Rock Cycle?
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The rock cycle below shows the life cycle of the three
rocks and how they are related to each other.
Assignment
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Nothing to Add to Your Timeline
Practice Problems
1.4 Questions
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Pg. 318 #1-9