Transcript Chapter 3 – The Dynamic Earth Section 1: The Geosphere

Chapter 3 – The Dynamic Earth
Section 1: The Geosphere
1. Describe the composition & structure of the
Earth
2. Describe the Earth’s tectonic plates
3. Explain the main cause of earthquakes & their
effects
4. Identify the relationship between volcanic
eruptions & climate change
5. Describe how wind & water alter the Earth’s
surface
The Earth as a System
• Earth consists of rock, air, water, & living
things that interact with each other
AIR
• Divided into 4 parts:
WATER
LIVING THINGS
ROCK
The Earth as a System
• Geosphere
– Solid portion consisting of rock
– Extends from center of core to surface of crust
• Atmosphere
– Mixture of gases
– Most found in first 30 km above Earth’s surface
• Hydroshpere
– All water on or near surface
– Most is oceans
• Biosphere
– Where life exists
– Extends from 9 km above surface to bottom of ocean
Discovering Earth’s Interior
• Seismic waves used
to study interior of
Earth
• Seismic waves
Earthquake
– Travel through
Earth’s interior during
earthquakes
– Altered by type of
material they move
Seismic
– Changes in speed & wave
direction measured
when passing
through different
layers
Composition of the Earth
• Divided into three
layers based on
composition
– Crust
– Mantle
– Core
• layers become
progressively
denser toward
the center
Crust
Core
Mantle
Crust
• Thin, outermost layer
– 5 to 8 km beneath oceans
– 20 to 70 km beneath
continents
• Solid, brittle
• Composed of lightweight
elements
• Makes up less that 1% of
Earth’s mass
Mantle
• Layer between crust &
core
• Composed of rock with
medium density
• Contains iron-rich
minerals
• Makes up 64% of Earth’s
mass
• Approximately 2900 km
thick
Core
• Innermost layer
– Liquid outer core
• Super-heated molten lava
• Composed of liquid nickel
& iron
– Solid inner core
• Sphere of solid nickel &
iron
• Consists of densest
elements
• Radius approximately
3400 km
Solid
inner
core
The Structure of the Earth
• Divided into 5
layers based on
the physical
properties
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner Core
Lithosphere
• Composes crust &
upper part of mantle
– 15-300 km thick (9185 mi)
• Divided into large
pieces called tectonic
plates
– May be oceanic or
continental
– Slide on fluid portion
of mantle
– Movement can cause
earthquakes
Asthenosphere
• Beneath lithosphere
– 250 km thick (150 mi)
• Solid, plastic-like
material of mantle
– Made of rock that
flows
– Due to temperature &
pressure
• Allows for movement
of tectonic plates
Mesophere
• Lower part of
mantle
• More solid & rigid
than asthenosphere
due to increased
pressure
– Can’t flow
Lithosphere
Asthenosphere
Mesosphere
Outer Core
Inner Core
Outer Core
• Super-heated molten
lava
– Composed of liquid nickel
& iron
– 4000 to 9000 °F
• Source of Earth’s
magnetic field
– Creates protective bubble
– Deflects Sun’s solar winds
Inner Core
• Solid ball
• Composed of nickel
& iron
• 9000 °F &
45,000,000 psi
• Rotates in liquid
outer core
Plate Tectonics
• Large, irregularly shaped slabs of rock
• Composed of oceanic & continental
lithosphere
– Continental rocks
• Lightweight minerals (quartz, feldspar)
• Thicker crust
– Oceanic rocks
• Heavier, denser basltic rocks
• Thinner crust
Major & Minor Tectonic Plates
Plates move in different directions and speeds, thus crash
together, pull apart or side swipe each other like cars in a
demolition derby
Plate Boundaries
• Most geologic activity occurs where plates meet or
divide (called boundaries)
• Movement of plates creates 3 types of tectonic
boundaries
– Convergent – plates collide, move into one another
– Divergent – plates move apart
– Transform – plates move sideways in relation to one
another
• Movement of tectonic plates causes
– Mountain formation
– Earthquakes
– Volcanic eruptions
Plate Tectonics and Mountain
Formation
• Plates collide, crust
thickens
• Rocks break & buckle
– Continental plate folds
into huge mountain
– Oceanic plate forms
trench
• Examples
– Rocky mountains (N.
America)
– Himalaya mountains
(Central Asia
Earthquakes
• Faults – breaks in Earth’s
crust where plates slide past
each other
• Rocks under stress break off
triggering ground vibrations
- called earthquakes
• Magnitude (Richter Scale)
–
–
–
–
Measure of energy released
2.0 – smallest felt
9.5 – largest recorded
Increase of 1 whole number
= 31.7 times more energy
Where Earthquakes Occur
Most occur at or near plate boundaries
Earthquake Hazard
• Earthquake hazard level determined by past &
present seismic activity
• Hazards (effects) include
– Ground shaking (building damage/settling of ground
beneath to different level)
– Ground displacement
– Flooding (breakage of levies, dams, Tsunamis)
– Fire (broken gas & power lines)
• Human hazards due to man-made structures
– Being crushed, buried or burned or drowning
• National Hazards Maps used by cities, counties &
local governments to update & create more
stringent building codes
Volcanoes
• Mountains built from
magma (molten rock)
• Magma rises to
surface from interior
• Most common at
convergent or
divergent plate
boundaries
• Can occur on land or
in oceans
Block between separating faults cracks,
drops into asthenosphere forming a rift.
Magma seeps upward to fill in crack
Volcanoes: The Ring of Fire
North American Plate
Eurasian Plate
South American Plate
• Majority of
active
volcanoes on
land located
along tectonic
plate
surrounding
the Pacific
Ocean
Pacific Plate
Australian Plate
Antarctic Plate
Local Effects of Volcanic Eruptions
• Clouds of hot ash, dust, & gases flow down the
slopes of volcanoes searing anything in its path
– Obscures sunlight, killing plants & animals
• Volcanic ash mixes with water producing
mudflows
– Water contamination
– Land contamination
• Collapse of buildings, burying of crops, & damage
to vehicle engines due to falling ash
Global Effects of Volcanic Eruptions
• Can cause changes in Earth’s climate
• Ash & sulfur-rich gases reach upper
atmosphere & reduce sunlight reaching
Earth’s surface
• Reduction in sunlight reduces average global
temperatures
Erosion
• Process resulting in materials of the Earth’s surface
being loosened, dissolved or worn away &
transported from one place to another by natural
agents such as wind, water, ice or gravity
• Water erosion
– Rivers carve deep canyons or gorges into bedrock
– Depositing of dust, pebbles, rocks forms new land areas
– Oceans erode coastlines
• Wind erosion
– Removal of most fertile part of soil lowering soil
productivity
– Creates sand dunes