The Dynamic Earth
Unit 3
3-1 The Earth as a System
Earth consists of rock, air, water, and living things; all interact
with each other.
• Earth system into four parts:
• -The Geosphere (rock)
• -The Atmosphere (air)
-The Hydrosphere (water)
• -The Biosphere (living things)
The Earth as a System
The Geosphere
• -Mostly solid, rocky part of
the Earth.
• -Extends from the core to
the crust.
• -Atmosphere is a mixture of
gases that makes up the air
• we breathe.
The Hydrosphere
• -Made up of all the water on
or near the Earth’s surface.
• -Oceans cover nearly threequarters of the globe.
• -Water is also found in the
atmosphere, on land, and in
the soil.
The Biosphere
• -Part of the Earth where life
• -Thin layer that extends from
about 9 km above the Earth’s
surface to the bottom of the
-Made up of parts of the
geosphere, atmosphere,
and hydrosphere
Discovering Earth’s Interior
• -Seismic waves are used to
learn about Earth’s interior.
• -Seismic waves travel
through Earth’s interior
during an earthquake.
• -The speed and direction of
seismic waves reveal the
different layers of the Earth.
The Composition of the Earth
Earth is divided into three layers:
•The crust
•The mantle
•The core
• -layers are progressively denser
• toward the center of the Earth.
The Crust
• -Thin, solid outermost layer
of the Earth.
• -Makes up less than 1
percent of the planet’s
• -Is 5 km to 8 km thick
beneath the oceans and 2070 km thick beneath the
The Mantle
• -Layer of molten rock between
the Earth’s crust and core.
• -Makes up 64 percent of the
mass of the Earth.
The Core
-Central part of the Earth below
the mantle.
-composed of nickel and iron.
-estimated temperature: btw
4,000°C to 5,000°C
- is solid because of enormous
Earth’s Structure
Earth can be divided into five
layers based on physical
-Lithosphere: solid, outer layer
of the crust and rigid upper
part of the mantle.
-is divided into huge pieces
called tectonic plates.
Earth’s Structure (cont’d)
-Asthenosphere: solid, plastic
layer of the mantle beneath
the lithosphere.
-made of slowly flowing
mantle rock, which allows
tectonic plates to move on
top of it.
-Mesosphere: lower part of
the mantle
Plate Tectonics
• Divisions of lithosphere.
• Glide across the asthenosphere.
• Major plates: Pacific, North
America, South America, Africa,
Eurasian and Antarctic.
Plate Boundaries
• Site of major geologic activity.
• Plates may collide, pull apart, or
“slip” past one another.
• Forces may result in
earthquakes, volcanoes or
mountain building.
• Faults are breaks in the crust.
• Slippage along faults vibrate
crust create earthquakes.
• Richter scale quantifies
magnitude earthquake energy.
-smallest magnitude: 2.0
-largest magnitude: 9.5
• Most active fault in N.A.: San
Andreas along California.
Where do Earthquakes Occur?
FYI: Earthquake Hazard
• Scientists cannot predicts when earthquakes will take place.
However, they can help provide information about where
earthquakes are likely to occur helping people prepare.
• An area’s earthquake-hazard level is determined by past and
present seismic activity.
• Earthquake-resistant buildings, built in high risk areas, are
slightly flexible so that they can sway with the ground motion
preventing them from collapsing.
Plate Tectonics and Mountain Building
• -Colliding plates form
mountain ranges
• Ex. The Himalaya Mountains
Mountain built from magma.
Can occur on land or in the sea.
Often located near tectonic plate
boundaries- plates are either
colliding or separating from one
Majority of active volcanoes on land
are located along tectonic plate
surrounding the Pacific Ocean.
Volcanoes: The Ring of Fire
Local Effects of Volcanic Eruptions
• -Clouds of ash, dust, and gases can flow down the slope of a
volcano at speeds of up to 200 km/hr.
• -Can burn everything in its path.
• -Volcanic ash mixed with water can produce mudflows.
• -Falling ash can cause buildings to collapse under its weight,
bury crops, damage the engines of vehicles, and cause
breathing difficulties.
Global Effects of Volcanic Eruptions
• -Major eruptions can change Earth’s climate for several years.
• -Clouds of volcanic ash and sulfur rich gases may reduce the
amount of sunlight that reaches the Earth’s surface.
• -Reduction in sunlight can cause a drop in the average global
surface temperature.
• -Process in Earth’s surface is
loosened, dissolved, or worn
away and transported by wind,
water, ice or gravity.
• -Wears down rocks and makes
them smoother with time
(reason why older mountains
are smoother than younger
Water Erosion
• -Rivers and oceans can
produce major changes on
Earth’s surface.
• -Waves from ocean storms
can erode coastlines.
• -Rivers can carve deep
gorges into the landscape.
Wind Erosion
• -At beaches and in deserts,
wind can blow soil away
• -Soft rocks, such as
sandstone, erode more
easily than hard rocks, such
as granite do.
Sect 2: The Atmosphere
• Mixture of gases:
Nitrogen (N₂)- 78%
Oxygen (O₂)- 21%
CO₂, H₂O, argon- 1%
• Insulates the earth from
heat and cold.
• Held in place by gravity
Layers of the Atmosphere
• Troposphere: closest to surface, site
of weather.
• Stratosphere: above the
troposphere, site of ozone
-ozone (O₃) protects against
harmful UV radiation from
• Mesosphere: coldest layer.
• Thermosphere: lowest layer is
ionosphere- site of aurora borealis
Energy in The Atmosphere
Energy from the sun is
transferred as heat by:
1. Radiation: across space.
2. Conduction: warm to cold.
3. Convection: air molecules
-hot air rises, cold air sinks.
The Greenhouse Effect
• Process in which gases trap heat
near the Earth’s surface.
-sunlight heats the surface
the day.
-some of the heat escapes back
into space.
-remainder of heat is trapped by
greenhouse gases (methane, CO₂,
nitrous oxide, water vapor).
Sect 3: The Hydrosphere and Biosphere
• Hydrosphere: includes all water
on or near Earth’s surface…
-oceans, lakes, icecaps, soil, clouds.
The Water Cycle
• Continuous movement of water
between air and land.
• 3 major processes:
-evaporation: liquid to vapor.
-condensation: vapor to droplets, forms clouds.
-precipitation: rain, snow, sleet,
• Single, interconnected body of
• Covers 70% of planet.
• Largest ocean: Pacific
-deepest point: Challenger Deep
-currents move clockwise north of
equator; counterclockwise south
of the equator.
Oceans (cont’d)
• 2nd largest ocean: Atlantic
• Smallest ocean: Arctic
-unique feature: pack ice covers
much of ocean’s surface.
Ocean Water
• Contains dissolved salts, most
of which is sodium chloride.
• Salinity: concentration of all
salts in water.
-lower where fresh water flows
into ocean.
-higher where water evaporates
Ocean Zones
• Surface zone: warm top layer;
currents mix warm and cool
• Thermocline: boundary
between warm and cold water;
temperature drops faster with
depth than other zones.
• Deep zone: bottom zone with
coldest temperatures.
Ocean Currents
• Surface: wind driven, result
from global winds.
-may be warm or cold.
-can flow for hundreds of km.s
ex. Gulfstream
-influence climate of land.
• Deep: flow slowly on ocean
-cold polar water sinks, moves
toward the equator.
Global Temperature Regulator
• Ocean waters absorb, store
energy from sunlight.
• Water absorbs, releases heat
more slowly than land, results in
slower atmospheric temperature
• Temperature regulation prevents
extremes on Earth.
Fresh Water
• Contains insignificant amounts
of salts.
• ≈ 3% of all water.
• Most is locked up in icecaps,
• Liquid form is found in lakes,
rivers, wetlands, the soil,
River Systems
• Network of streams that drains
an area of land.
• Contains all of the land drained
by a river, including the main
river and its tributaries: small
streams that empty into a river.
• Mississippi River system covers ≈
40% of the contiguous U.S.
• Area underground that collects
rain, melting snow.
• Less than 1% of all water.
• Fulfills the human need for fresh
drinking water, supplies agricultural
and industrial needs.
• Aquifers: rock layer that stores
and allows the for the flow of
-recharge zone: surface of land
where water enters aquifer.
The Biosphere
• Narrow layer of planet where
life is found (includes
geosphere, lower atmosphere,
• Closest to surface because of
ample sunlight there.
• Dependent on gravity, water,
Energy Flow Through the Biosphere
• Begins as sunlight trapped by
plants in photosynthesis.
• Dead organisms are broken
down, its energy and nutrients
are passed on to others.
• Recycling of nutrients and
energy flow make life possible.
Mount St. Helens, Washington State
Mount St. Helens, Washington State

ES 3 The Dynamic Earth