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APES
Ms. Tooker
2015
Earth Science Concepts

 Geologic time scale
 Plate tectonics
 Earthquakes
 Volcanism
 Seasons
 Solar intensity
 Latitude/longitude
Geologic Time Scale

Two time scales are used to measure the age
of Earth.
Sequence of layering of the rocks (strata)
and evolution of life
Radiometric time scale-natural
radioactivity of chemical elements in rocks
Geologic Time Scale

Organized into various units according to
events that took place in each period
Usually separated by major geologic or
paleontological events (mass extinctions)
 Largest unit of time- eon
Eon Eras Periods Epochs Stages

Geologic Time Scale

Key Principles of the Geologic Time Scale

Rock layers (strata) are laid down in
succession with each strata representing a
“slice” of time.
The principle of superposition- any given
layer is probably older than those above it
and younger than those below it.
Is the Geologic Time Scale
perfect??

NOOOO!!!
Layers are often eroded, distorted, tilted, or
uneven
Layers laid down at the same time in
different areas can have entirely different
appearances
A layer from any given area represents only
part of Earth’s history
Earth Structure

 Formed 4.6 billion years ago
 Third planet from the sun in the solar system
 Only planet known to support life
Earth Structure

 Biosphere- includes all forms of life (plants and
animals) both on land and in the sea
 Hydrosphere- includes all forms of water (fresh and
saltwater, snow, ice)
 Lithosphere- includes the outermost shell of the
planet (crust and upper mantle), approximately 62
miles thick
Crust

 Makes up 0.5% of Earth’s total mass
 Floats on top of the mantle
 Oceanic crust





From Earth’s surface to 7 miles down
Relatively cold
Rocky
Brittle
Fractures easily in earthquakes
Continental Crust

 Extends from Earth’s surface to 20-30 miles down
 Appears stratified (layered)
 Composed of volcanic, sedimentary, and granitetype rocks
 Older areas may be metamorphic
Mantle

 Most of Earth’s mass
 Composed of iron, magnesium, aluminum, and
silicon-oxygen compounds
 Over 1800˚F
 Mostly solid
 Upper third (asthenosphere) is more plastic-like


Plate Tectonics

 Continental drift theory- 1915, Alfred Wegener
 All present-day continents originally formed one
landmass (Pangaea).
 Based on:
 Fossilized tropical plants discovered beneath
Greenland’s icecaps
 Tropical regions on some continents has polar climates
in the past, based on paleoclimatic data
 The continents fit together like pieces of a puzzle

Plate Tectonics

 Seafloor Spreading Theory- 1960s
 Alternating patterns of magnetic properties were
discovered in rocks found on the seafloor.
 Dating of the rocks indicated that as one moved away
from the ridge, the rocks became older.
 New crust was being created at volcanic rift zones.

Plate Tectonics

 Earth’s plates float and move on the viscous
asthenosphere
 Subduction zones- where two plates meet and move
towards each other
Earth’s Major Plates

Transform Boundaries

 Occur where plates slide past each other.
 Friction and stress buildup from the sliding plates
and earthquakes occur
 Example: San Andreas Fault (Pacific Plate and North
American Plate)
Divergent Boundaries

 Occur where two plates slide apart from each other
with the space that was created being filled with
molten magma from below.
 Can create massive fault zones in the oceanic ridge
system-frequent oceanic earthquakes
 Example- Mid-Atlantic Ridge and the East Pacific
Rise
Convergent Boundaries

 Occur where two plates slide toward each other,
forming a subduction zone (one plate moving under
the other) or an orogonic belt (two plates collide and
compress)
Oceanic-Continental
Convergence

 Subduction zone- basaltic oceanic crust is more
dense than granite continental crust.
 Examples- deep ocean trenches, stratovolcanoes and
Volcanic Mts. on Land. ex.
 Cascade Mountains in the Pacific Northwest US
Oceanic-Oceanic Convergence

 An island arc (curved chain of volcanic islands rising
from the deep seafloor and near a continent)
 Created by subduction processes
 Examples- Japan, Aleutian Islands in Alaska
Continental-Continental
Convergence

 Mountain ranges are formed when plates collide
 Earth’s crust is compressed and pushed upward
 Examples- Himalayas

Earthquakes

Two classes of seismic waves: body waves
and surface waves
 Body waves travel through the interior of
Earth
 Two types of body waves:
 P waves
 S waves
Earthquakes

P waves:
 Travel through Earth
 Caused by expansion and contraction of
bedrock
Earthquakes

 S waves:
 Produced when material moves either vertically
or horizontally
 Travel only within the uppermost layers of
Earth (along its surface)
Earthquakes

 Surface Waves:
 Produce rolling and/or swaying motion and are
slower than P or S waves.
 Cause ground motion and damage.
Earthquakes

 The severity of an earthquake depends upon:
 The amount of potential energy that has been
stored
 The distance the rock mass moved when the
energy was released
 How far below the surface the movement
occurred
 The makeup of the rock material
The Richter Scale

Tsunamis

 A series of waves created when a body of water is
rapidly displaced, usually by an earthquake
 Generated when plate boundaries move abruptly
move
 Subduction-zone-related earthquakes generate the
majority of all tsunamis

Volcanoes

 Active volcanoes produce magma (melted rock) at
the surface.
 About 95% of volcanoes occur at subduction zones
and mid-oceanic ridges
 About 5% occur at hot spots
 Produce ejecta (lava rock and/or ash)
 Molten lava
 Toxic gases- steam, carbon dioxide, sulfur dioxide
Atmospheric Effects of Volcanoes

General Volcano Structure

Seasons, Solar Intensity,
and Latitude

 Factors that affect the amount of solar energy at the
surface of Earth:
 Earth’s rotation (once every 24 hours)
 Earth’s revolution around the sun (once per year)
 Atmospheric conditions
Summer Solstice

 Sun rises higher in the sky
 Stays above the horizon longer
 The sun’s rays strike the ground more directly (less
of an angle)
Winter Solstice

 Northern hemisphere is titled away from the sun
 The sun rises lower in the sky
 Stays above the horizon for a shorter period of time

 Earth is closest to the sun during the Northern
Hemisphere winter (Dec.-Feb.)
 Earth is farthest away during the Northern
Hemisphere summer (June-Aug.)
 Seasons are NOT caused by Earth’s distance from
the sun!!
 Seasons are created by the angle of sunlight hitting
the Earth.