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Unit 5 G9: Geology
Transcript of Unit 5 G9: Geology
What can the past tell us about the future?
Fact or Fiction?
1.) An electron is the heaviest part of an atom.
2.) The atomic mass minus the atomic number equals the number of neutrons.
3.) Streak, luster and cleavage are a few of the ways to determine a mineral.
4.) The study of the Earth and its history is called biology.
5.) Minerals can be human made.
6.) Felsic lava is thinner and slower moving.
7.) Lava is below the Earth's surface.
8.) Most of the Earth's crust is covered by sedimentary rock.
9.) Strata are layers in igneous rock.
10.) Geodes are full of fossils.
11.) The Earth's surface is not moving according to the Plate Tectonic Theory.
12.) Relative dating identifies the actual dates on which the events occurred.
13.) The geological time scale is a summary of the Earth's past preserved by the rock record.
Forms a crytal
Metallic or Non-Mettalic
powder on ceramic plate
Cleavage (smooth) or fracture (rough)
Moh's Hardness Scale
How Minerals Form
1. Molten Rock:
As lava or magma cools, crystals form. Magma produces LARGE crystals since it is underground and cools slowly. Lava produces small crystals since it is above ground and cools quickly.
Fast cooling lava
Slow cooling magma
Salar de Uyuni, Bolivia
Lake dried 40,000 yrs. ago
Mammoth Hot Springs
Grand Prismatic Spring
Extreme UNDERGROUND tEMPERATURE/pRESSURE
3. Metamorphism: Minerals under Earth's surface undergoing high pressure and temperature can change into different minerals.
Under different conditions solution produce a variety of crystals. Evaporation leaves behind molecules which undergo crystalization. Minerals will also precipitate OUT of a solution if the solution is oversaturated.
What is a Rock?
Types of Rocks
Not always a "cycle"
Can be more of a "web"
All rocks do through changes due to geologic forces.
1. Weathering: process that gradually breaks down
materials such as rocks and minerals.
2. Erosion: process of moving sediment from one
place to another; usually by wind, water, gravity.
What 2 things drives the rock cycle?
Two Major Forces Behind Rock Cycle
The breaking down rocks by physical forces (ice, roots, abrasion).
The breakdown of rocks by chemical reactions
that change the rocks' make-up, or composition.
Sandstone: Most likely went through oxidation.
Both responsible for changing the shape of the Earth
tree roots, burrowed animals
freezing & Thawing
Types of Mechanical Weathering
process by which natural forces break down rocks
Abrasion: wearing down by friction
Exfoliation:outer layers flake off.
oxidation: when rocks are exposed to oxygen
Types of chemical Weathering
hydrolyosis: when acid rain reacts with rocks; can cause clays
living organisms: lichen secretes weak acid that changed rock composition .
carbonation: occurs when
Carbon dioxide dissolves on water;
forms a weak acid rain.
What is the point
of studying the past?
Does it matter if
we know about fossil evidence?
Types of Fossils
Mold & Cast
Carbon Film Fossil
Fossil Record shows....
Development of Life:
to multi-celled eukaryotes
Appearance & Disappearance
Provides information about
amounts of time species existed
Dave Martel, a paleontologist, finds this object in the middle of the Sahara desert. He tried dating the object through radiometirc dating but the minerals in the rock do not allow him to date the rock. What should he do???
Use Index Fossils
Certain organisms fossilized within the rock layers.
When certain index fossil found, you have an idea of general time period the other fossil comes from.
Characteristics of Index Fossils
1. Easily recognizable; unique
3. Widespread over land
4. Remains is species that only
existed for brief time so they
are only found in a few layers.
What might it mean if
the same index fossils are
found in rock layers in
different parts of the
Geologic Time Scale
Geologic Time Scale is divided by what geologic thing happened in a particular time.
How it works:
I. 4 Eons
A. Precambrian Time: single-celled organisms come into existence
2. Archaean Eon
B. Cambrian Time: life as we know it, 15 % of entire time of Earth's history)
1.Phanerozoic Eon: 542 million years ago to now
II. Phanerozoic Enon broken into Eras (eras based on animals that lived)
A. Paleozoic (Age of Fish)
B. Mesozoic (Age of Dinosaur)
C. Cenozoic (Age of Mamals)
III. Eras broken into periods (11 in Phanerozoic Era)
IV. Periods broken into epochs
Geologic Time Scale is dependent on Stratigraphy which is the study of rock layers and fossils contained
inside of them.
Earth on the Move
Noticed similariteies in fossils across the Atlantic.
Saw that contintents "fit."
Pangea broke into Laurasia and Gondwanaland.