Download A Review of the Earth Notes

Class Notes
After class, review your notes and jot
questions and memory joggers in the narrow
column that help connect ideas listed in the
notes section. When you're studying, you will
look at these cues to help you recall the
salient facts in your notes, so keep that in
mind when you create your cues.
Name:
Class:
Block:
Date:
Topic: Unit 2 A Review of our Earth
Questions/Main Ideas/Diagrams
Notes:
What is a Geological Timescale?
 A scale of the history of the earth, supported by
geological/archeological evidence.
What are two ways that scientists can tell how old the earth is?
 Radiometric dating and Relative dating using fossils.
What is Relative Dating of Fossils?
 Using The law of superposition to compare ages of fossils.
What is radiometric dating?
 The use of isotopes (like carbon 14) to tell us the absolute date
of a fossilized organism.
How Old is the Earth?
 The Geologic Time Scale divides Earth’s history of 4.6 billion
years into subgroups that arrange events more orderly.
 The divisions are from largest to smallest length of time
 Eon
era
period
epoch
What might cause a major extinction?
 A catastrophic event might cause a major extinction, like the
dinosaurs.
What are some catastrophic events?
 Volcanoes
 Earthquakes
 Meteor showers
 Severe temperature changes (ice ages, global warming)
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 1
Questions/Main Ideas/Diagrams:
Notes:
Structure and Composition
 The Earth is comprised of four distinctive systems
 Atmosphere
 Hydrosphere
 Biosphere
 Lithosphere
 At the center of the Earth is the core, which consists mainly of
iron and is divided into 2 parts:
 Inner core
 Radius 1220 km
 6000 oC
 Solid iron
 Outer core
 Liquid iron
 Radius 3480km
 Contributes to magnetic field
The Mantle
 Next is the mantle a layer that makes up nearly 70% of Earth’s
interior. It is composed primarily of oxygen, silicon and
magnesium and is also divided into two parts:
 Asthenosphere- the solid, plastic layer of the mantle between
the mesosphere (lower part of the mantle) and the
lithosphere; made of mantle rock that flows very slowly which
allows tectonic plates to move on top of it
The Crust
 The crust is the top layer of the Earth.
 The upper mantle and the crust form the lithosphere (it is
divided in to huge pieces called tectonic plates).
Continental drift
 Alfred Wegener’s idea states continents have moved
horizontally along Earth’s surface to their present positions
Evidence that supports continental drift
1. Continents fit together like puzzle pieces.
2. Matching rock layers on Africa and South America
3. Matching fossils of land-based dinosaurs such as
Mesosaurus in the southern region of both Africa and South America.
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 2
Questions/Main Ideas/Diagrams:
Notes:
Plate Tectonics
 The lithosphere is broken into tectonic plates or lithospheric
plates.
 Each plate is roughly 100km thick and consists of uppermost
mantle with two types of crust on top: oceanic crust and
continental crust.
 Oceanic crust is thin (5-10km) but dense – rich in iron,
magnesium and silicon
 The continental crust is thicker (20-70km) and less dense
consisting of primarily calcium, sodium, potassium and
aluminum.
 Both types of crust can be found on a plate, but the denser
ocean crust is found below sea level. Earth has 7 major plates
and many minor plates.
 The places where plates meet are called the plate boundaries.
 Much of the geologic activity (earthquakes, volcanoes,
mountain formation) takes place at the boundaries between
tectonic plates.
 There are three different types of boundaries:
1. Divergent boundaries
2. Transform boundaries
3. Convergent boundaries
Divergent Boundaries
 Divergent plates are where two plates move apart.
 This is also known as floor spreading.
 A rift occurs and magma moves up from the mantle and cools
as it reaches the surface creating new crustal material.
 Mid Atlantic Ridge (causing Atlantic Ocean to grow larger)
Convergent Boundaries
 Convergent plates are when two plates collide
 Crust is destroyed & recycled back into the interior of the
Earth
 The denser plate (oceanic/basaltic) slides under the less dense
plate (continental/granitic)
 Oceanic-Continental Convergence - When an oceanic plate
pushes into and subducts under a continental plate, the
overriding continental plate is lifted up and a mountain range
is created. (oceanic is more dense and sinks)
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 3
Questions/Main Ideas/Diagrams:
Notes:
 Oceanic-Oceanic Convergence - When two oceanic plates
converge one is usually subducted under the other and in the
process a deep oceanic trench is formed (The Marianas
Trench); also results in the formation of undersea volcanoes
 Continental-Continental Convergence - When two continents
meet head-on, neither is subducted because the continental
rocks are relatively light and, like two colliding icebergs, resist
downward motion. Instead, the crust tends to buckle and be
pushed upward or sideways.
Transform boundaries
 Transform boundaries are where tectonic plates slide past
each other along transform faults.
 Transform faults are a type of strike-slip fault which means
that the movement of the fault is horizontal
 At times, movement along the fault is smooth and gradual. If
friction prevents the rocks from sliding by smoothly, pressure
builds up. This pressure or stress builds up to the point where
it suddenly snaps, creating a earthquake.
Earthquakes
 A fault is a break in the Earth’s crust along which blocks of the
crust slide relative to one another
 The point within Earth where faulting begins is the focus, or
hypocenter
 The point directly above the focus on the surface is the
epicenter
What are Seismic Waves?
 What causes earthquakes?
 Rocks in Earth’s crust is stressed and pulled
 This action stores elastic energy
 Once the build up of energy exceeds the strength of the rock
the energy is released
 The energy is released as seismic waves
 Body Waves
 Two types of Body Waves: P and S
 P Waves (Primary waves)
 Compression waves since they push and
pull rocks
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 4
Questions/Main Ideas/Diagrams:
Notes:
 Fastest moving seismic wave
 Able to move through solid rock and
fluids
 S Waves (Secondary waves)
 Slower than a P wave
 Can ONLY move through solid rock
 A seismograph is used to detect seismic waves
Measuring Earthquakes
 The Richter scale is a mathematical measurement of the
intensity of the ground shaking, as measured on a
seismograph. It is actually a measurement of the height
(amplitude) of the waves produced by the earthquake.
 The Richter scale grows by powers of 10. An increase of
1 point means the strength of a quake is 10 time greater
than the level before it. Here's how it works:
 An earthquake registering 2.0 on the Richter
scale is 10 times stronger than a quake
registering 1.0.
 A quake registering 3.0 is 10 X 10 or 100 times
stronger than a quake registering 1.0
 Earthquakes are measured by an instrument called a
seismograph. The seismograph records the motion of the
ground underneath it. By studying data from the seismograph,
scientists can figure out exactly where and when the
earthquake took place. They can also tell how big it was.
 The biggest earthquake ever recorded took place in
Chile on May 11,1960. It measured 9.5 on the Richter
scale and caused damage as far away as Japan.
 The world's second biggest earthquake, measuring 9.2
on the Richter scale, took place on Good Friday 1964 in
Prince William Sound, Alaska.
 The Modified Mercalli scales measures how people feel and
react to the shaking of an earthquake
 It is based on a series of key responses such as
people awakening, the movement of furniture, and
damage to structures. In general, the further one is
from the epicenter of an earthquake, the less
shaking is experienced.
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 5
Questions/Main Ideas/Diagrams:
Notes:
Tsunamis
 Earthquakes which occur on the ocean floor produce giant
sea waves called tsunamis. Tsunamis can travel at speeds
of 700 to 800 km per hour. As they approach the coast,
they can reach heights of greater than 20 meters.
 The Tsunami Warning Center is located in Hilo, Hawaii.
Case Study: Sumatra
 On December 26, 2004 an earthquake originated in the
Indian Ocean just off the western coast of northern
Sumatra. It had the second largest magnitude recorded on
a seismograph (9.1 and 9.3). The resulting tsunami killed
over 200,000 people. The coast areas of Indonesia,
Thailand, India and Sri Lanka were most affected.
Why Volcanoes Occur
 Temperatures in the mantle are hot enough to melt rock
into magma.
 Less dense than the solid rock around it, magma rises and
some of it collects in magma chambers.
 As the magma rises, pressure decreases allowing trapped
gasses to expand and propel the magma through cracks or
fissures in the Earth’s surface causing an eruption.
 Erupted magma is called lava.
Volcano Terms
 A vent is an opening through which eruptions take place.
 A crater is a basin like depression over a vent, at the
summit of a volcano
 A caldera is a depression larger than the original crater
(>1km. Diameter) that forms when the summit is blown
off, or when the volcano collapses into the empty magma
chamber. Example: Crater Lake atop Mt. St. Helens.
 Types of Volcanoes: Shield Volcanoes
o Shield Volcanoes are built up almost entirely of lava
flow, which pours out in all directions.
o This results in a flat, conical shape that looks a little
like a warrior's shield. Many of the world's largest
volcanoes are Shield Volcanoes.
o The Hawaiian Islands are a linear chain of them.
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 6
Questions/Main Ideas/Diagrams:
Notes:
 Types of Volcanoes: Stratovolcanoes (Composite)
o Stratovolcanoes (also called Composite Volcanoes)
are built up of alternating layers of lava
flow, volcanic ash and cinders.
o Stratovolcanes usually have large, steep sides and
symmetrical cones. They can get to be as high as
8,000 feet.
o Mt. Fuji in Japan and Mount St. Helens in the U.S.
are Stratovolcanoes.
o
 Types of Volcanoes: Cinder Cones
o Cinder Cones are the simplest type of volcano. They
are built up from blobs of lava ejected from a single
vent.
o Cinder Cones rarely get to be more than a thousand
feet high.
o Most famous cinder cone, Paricutin, grew out of a
corn field in Mexico in 1943 from a new vent.
Ring of Fire
 One major earthquake and volcano zone extends nearly all
the way around the edge of the Pacific Ocean. This zone
goes through New Zealand, the Philippines, Japan, Alaska
and along the western coasts of North and South America.
The San Andreas fault is part of this zone.
Case Study: Mount St. Helens
 Located in Washington State, Mount St. Helens erupted in
1980. The earthquake removed trees, increased soil
erosion, destroyed wildlife and polluted the air with gases
and ash. Other effects included mudflows, melting of
glacial ice and snow and clogged rivers that caused
flooding. Fifty seven people were killed.
Case Study: Mount Pinatubo
 Mount Pinatubo is part of a chain of composite volcanoes
on the west coast of the island of Luzon in the Philippines.
In June 1991, Mount Pinatubo erupted for 9 hours and
vented 18 million metric tons of sulfur dioxide into the
atmosphere which encircled Earth in three weeks after
reaching the stratosphere. This was the largest sulfur
dioxide cloud ever detected to date.
Summary, Reflection, Analysis
© 2004 AVID Center. All rights reserved.
Page 7