Download Unit 3 Study Guide

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Study Guide
Unit Test Study Guide:
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Geology
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Use the summary points below as a resource to help you study for our unit test at the end of the un
EXPLORING & CALCULATING DENSITY:
 Density is a measure of how much mass
there is in a volume of a substance.
 You can find the density in three different
ways:
o Using the formula.
o If you would like to find out the
density of an odd-shaped object
and you have a graduated cylinder
filled to let’s say 4 mL – drop the
odd-shaped object into the
graduated cylinder. The difference
between 4mL and the new
measurement on the graduated
cylinder would give you its volume.
You could use a balance to obtain
the mass, then use the above bullet
for the density equation.
o Take two or more liquids and place
them in a container together to see
which is more or less dense. The
liquid(s) that are closer to the
bottom are more dense. The
liquid(s) that are closer to the top
are less dense.
least dense (floats)
most dense (sinks)
EARTH’S LAYERS:
Facts About the layers of the Earth:

The four main layers of the Earth:
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Density, temperature and pressure
increases as you move inside the Earth
from the crust.
The crust includes dry land and the ocean
floor.
The crust and inner core are made of solid
rock.
The outer core is liquid.
The mantle is the largest layer and is
broken up into three layers, which are
upper mantle (solid), asthenosphere
(molten/melted rock) and the lower mantle
(mostly solid).
The outer core is made of liquid nickel while
the inner core is made of solid nickel and
iron.
CONVECTION CURRENTS IN THE MANTLE:
 Heat from the core and lower mantle causes
convection currents in the mantle.
 The process works like this:
1. The lower mantle and core heat up the
magma in the asthenosphere.
2. The magma rises once it is heated b/c it is
less dense.
3. Since the lithosphere is composed of the
two coolest layers, when the magma rises
it is cooled off by the lithosphere, so it sinks
b/c the cooling has made it more dense.
4. The process starts all over again.
lower
THEORY OF PLATE TECTONICS:
The theory of plate tectonics explains the formation, movement and subduction of Earth’s plates.

or come together 

causes the formation of
mountains (continental crust)

causes volcanoes to form
(oceanic + continental crust)
this is subduction!!!
slide past each

causes stress in the crust

causes earthquakes when stress
is released
DRIFTING CONTINENTS:
Scientist Alfred Wegener hypothesized that all continents had once been joined together in a single landmass and
have since drifted. Wegnener used four pieces of evidence to support his hypothesis:
 The continents fit together like puzzle pieces. We call this supercontinent Pangaea.
 He found fossils of tropical animals and plants in arctic places.
 He collected evidence of historic climate data indicating an ice age had indeed taken place – movement of
the poles.
 He noticed that the pattern of mountains on different continents lined up perfectly if you put the continents
together like puzzle pieces.
FORCES IN THE EARTH’S CRUST & FAULTS:

When Earth’s plates move, rocks are pushed and pulled. The pushes and pulls are called stress.
There are 3 types of stress in the crust:
divergent movement

rock is pushed together
convergent movement
rock slides past each other
transform movement

Faults usually occur along plate boundaries,
motion push or pull the crust so much that the crust
types of faults: normal faults, reverse faults and
Over millions of years, the forces of plate movement can
landforms such as mountains.
Strike-slip
fault
Rock is pulled apart
reverse
fault


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plates move apart
other
cause mid-ocean ridges
cause sea-floor spreading
you can get volcanoes &
mountains this way
normal
fault

where the forces of plate
breaks. There are three main
strike-slip faults.
change a flat plain into
EARTHQUAKES:

When tension builds up in the Earth’s crust, sometimes an earthquake happens along with a fault.

Earthquakes are measured using seismographs. We use the information from the seismograph to
assign the earthquake a number on the Richter Scale.

During an earthquake, seismic waves cause the seismograph to vibrate. The recording of the level of
vibrations (magnitude) helps scientists to determine the severity of the earthquake.


Seismic waves carry energy from the focus, through rock in the crust and onto the Earth’s surface.
There are 3 types of seismic waves:
primary waves compress and
expand like an accordion;
they move the fastest of
the three types
secondary waves vibrate
from side to side or up
and down in an “s”
motion
surface waves roll the ground
with a wave-like motion.
They are the slowest, but
most destructive!
VOLCANOES:

Volcanoes can occur as a result of divergent and convergent plate movement. They can also occur in
hot spots. A hot spot is an area of volcanic activity that is not near a plate boundary. When a hot spot
forms under a tectonic plate, the hot spot stays in one place, while the plate moves slowly over it. This
movement produces a chain of volcanoes. The Hawaiian Islands are a chain of volcanoes that formed
this way.
hot spot

crust
Volcanoes mostly occur at convergent boundaries where continental
meets oceanic crust. The more dense oceanic plates sink underneath the less dense continental
plates. This is called a subduction zone. The edge of the oceanic plate sinks into the mantle and
melts. The pressure and heat then build in this area, push through the mountain made from the
convergent plates and eventually will erupt to form a volcano (because pressure builds up).

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There is no difference between lava and magma. We just call it magma if it is below Earth’s surface
and we call it lava once it reaches Earth’s surface.
The Ring of Fire is an area in the Pacific Ocean that has many earthquakes and volcanoes. The map
below shows the Ring of Fire. You can see that it matches plate boundaries around the edge of the
pacific ocean. Nearly 75% of Earth’s volcanoes are located along the Ring of Fire.
SEA-FLOOR SPREADING

In sea-floor spreading, the sea floor spreads apart both sides of a mid-ocean ridge as new crust is
added. As a result, the ocean floors move like conveyor belts, carrying the continents along with
them.

Where the sea-floor separates (fault), ridges form on both sides. We call these ridges mid-ocean
ridges since they happen in the middle of the ocean floor. Sometimes the lava can cool over the
fault and that area becomes a volcano.

The oldest portion of the sea floor would be found farthest away from the mid-ocean ridge.
While the newest portion of the sea floor would be the part closest to the mid-ocean ridge.

Earth doesn’t grow or expand b/c as the sea floor moves apart in one area, on both sides there
are subduction zones sucking the ocean floor underneath the Earth to be recycled again because
of density.
WEATHERING, EROSION & DEPOSITION:
MINERALS:
Weathering breaks it down! Erosion carries it away!
Deposition piles it up and that is where it stays!
Weathering – the breaking down of rock
into sediments by ice, water or wind
Two types:
 mechanical or physical
Minerals – naturally occurring solids that have a
definite crystal shape and structure
Minerals are classified in five ways which are:
LUSTER
Cleavage & Fracture
How a mineral reflects
How the mineral breaks
HARDNESS
The results of scratching a
mineral against another
COLOR
STREAK
The powder that a mineral
leaves behind when
rubbed across a surface
A mineral’s color
The ROCK CYCLE:
The rock cycle describes how rocks are formed. All rocks are made up of sediments plus at least one type
of mineral. There are three types of rocks. They are:
Igneous Rocks
formed by heating and
cooling of molten/melted
rock
Extrusive – formed on Earth’s
surface by lava
Intrusive – formed inside
Earth’s surface by magma
Example: granite, obsidian
Sedimentary Rocks
formed by piling up of
sediments into layers
(compaction & cementation)


Can form on water or
land
Form from other rocks
being weathered
Metamorphic Rocks
formed by heat and pressure
below Earth’s surface
All metamorphic rocks were
previously some other type of
rock (sedimentary or igneous)
Example: marble, gneiss
Example: sandstone,
limestone
SOIL:
Soil is a mixture of weathered bedrock plus humus (decayed organic material)
Bedrock - (the Earth’s crust that has not been weathered)
Organic – any material that was is living or a part of something living
THE LAW OF SUPERPOSITION:
 The law of superposition states that younger
sedimentary layers pile up on top of older layers.
 Scientists use the order of the layers to make
inferences about the Earth’s history.
 Index fossils are fossils that date a certain period in
history. A fossil’s age is the same as the layer where it
is found.
Horizon O
 Intrusions are cooled magma that has oozed out of the asthenosphere and lays
across or touches already existing sedimentary layers. An intrusion is ALWAYS
YOUNGER than any layer that it touches or cuts across!
Regular sedimentary layers:
Sedimentary layers with an intrusion: