The Physical World Chapter 2

Our Solar System Earth is part of a larger physical system that contains other planets, moons and stars.

The Planets Planets – largest objects in the solar system Dwarf 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 Meteoroids Asteroids – small, irregularly shaped, planet-like objects Comets – 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 Earth Earth’s surface is a complex mix of landforms and water systems

Water, land and Air Hydrosphere – surface of the earth made up of water, about 70 percent Lithosphere – the earths crust, about 30 percent of the earths surface Atmosphere – 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.

Landforms Landforms – 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 Depths Highest Point – Mount Everest – 29,028 ft Lowest Point – Mariana Trench – 35,827 ft below sea level

2. Forces of Change The Earth’s internal and external structure, including the tectonic plates, is responsible for the creation of the continents, oceans and mountain ranges.

A Layered Planet Core – hot, solid center of Earth Mantle – thick layer of hot dense rock, middle layer of earth Crust – rocky shell forming the Earth’s surface

Plate Movement Continental Drift – theory that the continents were once joined and then slowly drifted apart Pangaea – Supercontinent Plate Tectonics – scientists theorize that plates moving slowly around the globe have produced Earth’s largest features Magma – molten rock

Internal Forces of Change Plate Tectonics is responsible for folding, lifting, bending and breaking parts of the Earth’s surface.

Colliding and Spreading Plates Mountains 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 Faults Folds – 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.

Earthquakes Earthquakes are sudden, violent movements of tectonic plates along a fault line.

Volcanic Eruptions Volcanoes are mountains formed by lava or by magma that breaks through the Earth’s crust.

External Forces of Change External forces such as weathering and erosion also shape the surface of the Earth.

Weathering Weathering – breaks down rocks Erosion – wears away the Earths surface

Glacial Erosion Glaciers – 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 glaciers Sheet glaciers – flag, broad sheets of ice. Ex. Greenland and Antarctica. Mountain glaciers – located in high mountain valleys where the climate is cold.

Water Erosion Water 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 Cycle The 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 Water Salt water covers much of the earth’s surface.

Oceans About 97 percent of Earth’s water is ocean water This water is salt water Too salty for drinking, farming Desalination – turning ocean water into freshwater

Bodies of Freshwater Although there is a small amount of freshwater on Earth, it is necessary to sustain life.

Lakes, Streams and Rivers Only about 3 percent of Earth’s water is freshwater Lakes, Streams and Rivers contain less than 1 percent of Earth’s water Groundwater – 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