Third Rock From the Sun

Chapter 2Unit 1

Earth and the Solar System

• Earth has one moon, which revolves around the planet about once a month.

• The sun is at the center of our solar system.Planets1. Terrestrial planets- Mercury, Venus, Earth, and Mars-

called this because they have solid rocky crusts.2. Gas Giant Planets- Jupiter, Saturn, Uranus, and

Neptune- farther from sun and more gaseous and less dense.

Pluto is the exception- ball of ice and rock

What conditions on gas giant planets make them unsuitable for life to exist there?

Getting to Know Earth

• Surface of Earth is about 30 % land and about 70% water.

• Atmosphere is about 78% nitrogen and 21% oxygen, and about 1% other gases, such as argon.

• The Earth has landforms such as continents, mountains, hills, plateaus, valleys, and plains. The part of a continent that extends underwater is called a continental shelf.

Getting to Know Earth

• Highest point on Earth is Mount Everest at 29,035 feet above sea level

• Lowest point of dry land is on the shore of the Dead Sea at 1,349 feet below sea level.

• The deepest known level of the ocean floor is the Mariana Trench at 35,827 feet below sea level.

It is 8.6 times saltier than the ocean. This salinity makes for a harsh environment in which animals cannot flourish, hence its name. People believe the mud has cosmetic and healing effects.

Structure

• Earth is composed of three layers: Core, mantle, and the crust.

• Many scientists believe that all the continents once were joined and have broken apart and drifted- this is called Continental Drift

• Plate tectonics- gradual movement of plates that come together and pull apart, pushing up mountains, creating volcanoes, and producing earthquakes.

Internal Change

• When Sea plates collide, they may create a chain of Islands. Ex: Ring of Fire

• Fault lines- cracks created in the Earth’s surface by plates being squeezed beneath.

• Earthquakes- sudden, violent movements along the fault lines. Ex. San Francisco and Los Angeles, Japan, and Haiti.

• Volcanic Eruptions- volcanoes are mountains formed by magma that has broken through the Earth’s crust.

External Forces of Change

Two types of Weathering:1. Physical weathering- occurs when large

masses of rock are broken down into smaller pieces.

2. Chemical weathering- changes the chemical composition of rocks.

Wind Erosion- Movement of dust, sand, and soil from one place to another.

Erosion

• Glacial Erosion- large bodies of ice that move slowly across Earth’s surface, carrying rocks and soil. Two types of Glaciers:A. Sheet glaciers- flat, broad sheets of iceB. Mountain glaciers- located in high mountain valleys.

Water Erosion- rain, rivers, streams, and oceans wear away soil and rock, often forming valleys and canyons.

Water Cycle

The part of the Earth covered by water is called the hydrosphere, with much of it being salt water, found in oceans, seas, and some lakes. The rest of the hydrosphere is the freshwater of lakes, rivers, and springs.

The Sun’s heat evaporates water, which remains in the air until the air cools. The cool air returns the water to Earth in the form of rain, snow, or sleet.

Bodies of Salt Water

• 97 % of hydrosphere is divided into four main oceans:A. AtlanticB. PacificC. IndianD. ArcticSeas, gulfs, and bays are also large bodies of salt water

partially enclosed by land.-demand for freshwater has led people to experiment

with desalination.

Bodies of Freshwater

• Only about 3% of the hydrosphere is freshwater, and most of it is frozen in glaciers and icecaps, inaccessible to people.

• Lake- body of freshwater completely surrounded by land.

• Streams- narrow bodies of water flowing through areas of land.

• Rivers- large streams that carry greater volumes of water• Groundwater- freshwater lying beneath the planet’s

surface. Ex: natural springs and handmade wells.