Chapter 2The Earth

Section I. Planet Earth What do you know about the Solar

System?

A. Our Solar System The sun is at the center of our Solar

System Sun creates a strong pull of gravity Keeps objects such as Earth revolving

around the Sun

Our Solar System Revolution – in astronomy, the Earth’s

yearly trip around the sun 365 ¼ days Why is the ( ¼ ) important to know??

Rotation – the Earths daily trip turning on its axis How long is a day?

In history…. People believed that the solar system

revolved around Earth Geocentrism Connected to religion

But it was Galileo (16th century) that actually fought for the now accepted theory that we were the ones moving Heliocentrism

What’s the idea behind the theories? Why would people think we were

geocentric?? Which theory would you side with if you

had to choose? What would happen without the sun?

The “Classical” Planets: Neighbors in Space Before it was believed we had nine

planets now we just classify eight Inner Planets (Terrestrial)

Mercury Venus Earth (only one with sustainable life) Mars

The “Classical” Planets: Neighbors in Space Outer Planets (Gas Giants)

Jupiter Saturn Uranus Neptune

All have moons except Mars & Venus There are also asteroids, comets and

meteoroids

Pluto……..planet?? Discovery Channel, August 24th, 2006 [Much-maligned Pluto doesn't make the

grade under the new rules for a planet: "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit.“]

[Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.]

B. Getting to know the Earth The earth is divided into categories

Hydrosphere – part of Earth made up of oceans, lakes, rivers, and other bodies of water

Lithosphere – part of Earth made up of continents and islands

Atmosphere – a layer of gases that surrounds the Earth

Biosphere – the part of the Earth that supports life

Hydrosphere = WATER Earth is 70% water

Lithosphere = Land Earth is 30% land

Atmosphere = Air Above earth’s surface you have a layer

of gases 78% nitrogen, 21% oxygen and the rest

argon and other gases Our natural vegetation is essential to the

recyclement of our oxygen

Biosphere = life The part of earth that supports life Life outside of the biosphere only exist

with mechanical life support system Space shuttle

Air + Land + Water =Biosphere! Bio=life! Hence, Biology….

C. Landforms Natural features of the earth’s surface

that vary in shape and elevation 4 major landforms-

Mountains Hills Plateaus PlainsAlso have valleys, canyons, and basins

All contain rivers, lakes and streams

Underground Landforms Landforms underwater are as diverse as

those found on dry land Range from flat plains to mountain

ranges, cliffs, valleys and deep trenches

Earth’s most visible landforms From space the most visible landforms are

the 7 continents Australia Antarctica Europe Asia North America South America Africa

**** Locate continents on your map ****

Continental Shelf Part of a continent that extends

underwater

Long narrow underground canyon (Pacific Ocean)

Section II. Forces of Change How does earth change? What processes are responsible for such

changes?

Forces of Change On the surface

Wind, water, etc Originate from the interior

Volcanic eruptions, earthquakes, etc

Earth’s Structure The earth is composed of three layers

Core Inner core is made up of iron and nickel

under enormous pressure Outer layer is liquid made up of melted

iron and nickel

Mantle Thick layer of hot dense rock Mixture of elements that continually

rises, cools, sinks, warms up and rises again

Responsible of 80% of heat generated from earth’s interior

Crust Broken up into more than a dozen great

slabs of rock called plates that rest (float) on a partially melted layer in the upper mantle

Carry the earth’s oceans and continents

Continental Drift TheoryPangaea Theory that all the continents were once

joined and slowly started to drift apart

Plate theory“Continental Drift” Pangaea – a gigantic supercontinent

that eventually broke apart (drifted) into smaller continents due to plate movement

Crust=Plates

Plate Tectonics Plates are continually moving At times they may crash, pull apart, grind

or slide past each other Constantly changing the face of the planet They push up mountains, create

volcanoes, and produce earthquakes Theory: heat rising from the core create

slow-moving currents within the mantle which then shift the plates around

Crust=Plates

Internal forces of change1. Colliding2. Subduction3. Accretion4. Spreading5. Folds6. Faults7. Earthquakes8. Volcanic Eruptions

1. Colliding Giant continental plate collide

Creates mountains Himalayas

2. Subduction A heavier sea plate dives beneath the

lighter continental plate Plunging into the earth’s interior, the

sea plate becomes molten material Then as magma it bursts through the

crust to form volcanic mountains Andes

3. Accretion Pieces of earth’s crust come together

slowly as the sea plate slides under the continental plate

Creates underwater mountains with steep sides and sharp peaks

Creates new land often island chain at the boundary

4. Spreading Sea plates pull apart Deep cracks (rift) allow magma from

within the earth to well up between the plates

Magma hardens to build undersea volcanic mountains or ridges

Spreading keeps Europe and N. Ame apart

5. Folds (bends) Moving plates squeeze the earth’s

surface until it buckles or creates folds in layers of rock

6. Faults Plates grind or slide past each other

creating cracks in earth’s crust When land can no longer be folded the

earth’s crust cracks and breaks into huge blocks

Small tremors occur San Andres Fault in CA

7. Earthquakes Sudden, violent movements of plates along a

fault line Dramatically change the surface of the land and

the floor of the ocean Happen when different plates meet each other.

Tension builds up as the plates stick. The strain becomes so intense that the rocks suddenly snap and shift. This releases stored up energy along the fault. Eventually the ground trembles as sends shock waves which are felt

Ring of Fire Earthquake and volcano zone

surrounding the Pacific Ocean Boundary where the plates that cradle

the Pacific meet the plates that hold the continents surrounding the ocean

8. Volcanoes Volcanoes are mountains formed by lava or

magma that breaks through the earth’s crust

Often rise along plate boundaries where one plate plunges beneath another

In such a process the rocky plate melts as it dives downward into the hot mantle. Pressure builds, a funnel is created and hot magma rushes to the surface. The lava will eventually create a volcano

Volcanoes As a moving plate passes over these hot

spots, molten rock flowing out of the earth’s surface may create volcanic island chains

Hawaiian Islands Molten rock may also heat underground

water causing hot springs or geysers Yellowstone

External Forces of Change Wind and water change the earth’s surface (two

processes) Weathering – process that breaks down rocks on

the earth’s surface into smaller pieces Erosion – wearing away of the earth’s surface by

wind, glaciers, and moving water1. Weathering2. Wind Erosion3. Glacial Erosion 4. Water Erosion

Weathering Either physical weathering or chemical

weathering Physical – when large masses of rock are

physically broken down into smaller pieces Water seeps into the cracks in a rock and freezes,

then expands and causes the rock to split Chemical – changes in the chemical makeup of

rocks (transforming their minerals or combining them) Water mixed with carbon dioxide from the air easily

dissolves certain rocks such as limestone

Wind Erosion Movement of dust, sand, and soil from

one place to another Can be devastating or beneficial

Dust Bowl China Yellow River basin is thickly

covered with loess (fertile yellow-gray soil deposited by wind)

Glacial Erosion Glaciers – large bodies of ice that slowly

move across the earth’s surface Glacial movements change the landscape by

destroying forests, carving our valleys, etc However, when glaciers melt and recede

they leave behind large pules of rocks and debris (moraines)

Moraines can form long ridges of land or create glacial lakes

Water Erosion Most significant cause of erosion Fast moving water – rain, rivers,

streams, and oceans – cuts into the land wearing away the soil and rock

The resulting sediment (small particles of soil, sand and gravel) act like sandpaper and cut away at land

Grand Canyon

Section 3 – Earth’s water Hydrosphere!! Almost all of the hydrosphere is salt

water found in the oceans, seas and seawater lakes

The remainder is freshwater found in lakes, rivers, and springs

Water Cycle Regular movement of water through

1. Evaporation – sun, changing liquid into vapor or gas

2. Condensation – excess water vapor changes into liquid form

1. Forms clouds

3. Precipitation – rain, snow, or sleet that sinks into the grounds and soon is evaporated again

Bodies of Salt Water (97%) Oceans

1. Pacific2. Atlantic3. Artic4. Southern 5. Indian

Seas, Gulfs, and Bays Desalination – conversion saltwater into

freshwater

Freshwater (3%) Lakes, Streams, and Rivers Groundwater – freshwater that lies beneath

the earth’s surface Comes from rain and melted snow that filter

through the soil and from water that seeps into the ground from lakes and rivers

Can use wells to tap into freshwater Aquifer – underground porous rock layer

saturated with water in the form of streams