The Physical World

Chapter 2

Our Solar SystemEarth is part of a larger physical system

that contains other planets, moons and stars.

The PlanetsPlanets – largest objects in the solar systemDwarf planets – small round bodies that

orbit the sun, but have not cleared the area around their orbits of other orbiting bodies.

Terrestrial Planets – have solid, rocky crusts. Ex. Mars, Earth, Venus, Mercury.

Gas Giant Planets – More gaseous and less dense planets. Ex. Jupiter, Saturn, Uranus and Neptune

Asteroids, Comets and MeteoroidsAsteroids – small, irregularly shaped,

planet-like objectsComets – made mostly of icy dust particles

an frozen gases, look like bright balls with long, feathery tails.

Meteoroids – chunks of space debris, chunks of rock and iron.

Getting to Know EarthEarth’s surface is a complex mix of

landforms and water systems

Water, land and AirHydrosphere – surface of the earth made

up of water, about 70 percentLithosphere – the earths crust, about 30

percent of the earths surfaceAtmosphere – layer of gases extending

above the planets surface.Biosphere – the part of the earth that

supports life, on or close to the earths surface or in the atmosphere.

LandformsLandforms – natural features of the earth’s

surface. Continental Shelf – underwater extension of

the coast. Continental shelves slope out from land.

Continental Slope – sharp drop off to the ocean floor

Earth’s Heights and DepthsHighest Point – Mount Everest – 29,028 ftLowest Point – Mariana Trench – 35,827 ft

below sea level

2. Forces of ChangeThe Earth’s internal and external structure,

including the tectonic plates, is responsible for the creation of the continents, oceans and mountain ranges.

A Layered PlanetCore – hot, solid center of EarthMantle – thick layer of hot dense rock,

middle layer of earthCrust – rocky shell forming the Earth’s

surface

Plate MovementContinental Drift – theory that the

continents were once joined and then slowly drifted apart

Pangaea – SupercontinentPlate Tectonics – scientists theorize that

plates moving slowly around the globe have produced Earth’s largest features

Magma – molten rock

Internal Forces of ChangePlate Tectonics is responsible for folding,

lifting, bending and breaking parts of the Earth’s surface.

Colliding and Spreading PlatesMountains are formed in areas where giant

continental plates collide. Subduction – heavier sea plate dives

beneath the lighter continental plate. Accretion – as sea plate slides under

continental plate, debris buildup causes continents to grow outward.

Spreading – sea plates pull apart.

Folds and FaultsFolds – bends in layers of rock.Faults – cracks in earths surface.Faulting – occurs when earth cannot be

bent any further, crust cracks and breaks into huge blocks.

EarthquakesEarthquakes are sudden, violent

movements of tectonic plates along a fault line.

Volcanic EruptionsVolcanoes are mountains formed by lava or

by magma that breaks through the Earth’s crust.

External Forces of ChangeExternal forces such as weathering and

erosion also shape the surface of the Earth.

WeatheringWeathering – breaks down rocksErosion – wears away the Earths surface

Glacial ErosionGlaciers – large bodies of ice that move

across the Earth’s surface.Glacial movement changes the landscape.Moraines – large piles of rocks and debris

left behind by glaciersSheet glaciers – flag, broad sheets of ice.

Ex. Greenland and Antarctica. Mountain glaciers – located in high

mountain valleys where the climate is cold.

Water ErosionWater erosion begins when spring water

and rainwater flow downhill in streams, cutting into the land and wearing away the soil and rock.

Oceans also cause erosion by pounding the coastlines with their waves.

3. Earth’s Water

The Water CycleThe water cycle is the name given to the

regular movement of water. Earth’s water is constantly moving, from the

oceans, to the air, to the land and back to the oceans.

Evaporation – changing of liquid water into vapor.

Condensation – when warm air cools, it cannot retain all of its water vapor, so the excess water vapor changes into liquid water.

Precipitation – rain, snow or sleet

Bodies of Salt WaterSalt water covers much of the earth’s

surface.

OceansAbout 97 percent of Earth’s water is ocean

waterThis water is salt waterToo salty for drinking, farmingDesalination – turning ocean water into

freshwater

Bodies of FreshwaterAlthough there is a small amount of

freshwater on Earth, it is necessary to sustain life.

Lakes, Streams and RiversOnly about 3 percent of Earth’s water is

freshwaterLakes, Streams and Rivers contain less

than 1 percent of Earth’s waterGroundwater – freshwater that lies beneath

the Earth’s surface, comes form rain and melted snow that filter through the soil and from water that seeps into the ground from lakes and rivers.

Aquifer – underground porous rock layer often saturated by very slow flows of water