THE

PHYS

ICAL

WORLD

:

PLANET

EARTH

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AP T E R

2 S

E CT I O

N 1

OUR SOLAR SYSTEM

• Earth is a part of our solar system, which includes Earth and other planets that revolve around the sun

PLANETS

• Planets are large spherical bodies in our solar system

• There are at least 8 planets, and each follow their own orbital path around the sun

• Mercury, Venus, Earth, and Mars are the inner planets (nearest to the sun)• Earth is about 93 million miles away

• Jupiter, Saturn, Uranus, and Neptune are the outer planets (farthest from the sun)

• Jupiter is the largest planet, Earth is 5th largest, and Mercury is the smallest

• With the exception of Mercury and Venus, all the planets have moons, which are smaller spheres or satellites that orbit them• Ceres and Pluto are dwarf planets

• Two types of planets: terrestrial and gas giant planets

RECAP

• Which four planets are closest to the sun?

• What physical characteristics do the inner planets share? Outer planets?

ASTEROIDS, COMETS, AND METEOROIDS

• Asteroids are small irregular shaped, planet-like objects that revolve around the sun• Found mainly between Mars and Jupiter in the asteroid belt

• Comets are made of icy dust particles and frozen gases, which resemble bright balls with long feathery tails• Can travel in any direction to Earth

• Meteoroids are pieces of space debris—chunks of rock and iron • Earth’s atmosphere usually burns up meteoroids• It’s rare, but meteorites can sometimes strike• 1908 remote Russian forest region of Siberia

GRAPHIC ORGANIZER:FOUR COMPONENTS OF EARTH

Component Description

Hydrosphere

Lithosphere

Atmosphere

Biosphere

GETTING TO KNOW EARTH: WATER, LAND, AND AIR

• About 70 percent of Earth’s surface is water• Oceans lakes, rivers, and other bodies of water make up the Earth’s

hydrosphere

• About 30 percent of Earth’s surface is land, including continents and islands.• Land makes up the Earth’s lithosphere, the Earth’s crust • Also includes the land beneath the oceans (ocean basin)

• The air we breathe is part of Earth’s atmosphere, a layer of gases extending above the planet’s surface• Earth’s atmosphere includes 78 percent Nitrogen and 21 percent

oxygen, as well as small amounts of argon and other gases

• The part of Earth that supports life is called the biosphere

RECAP

LANDFORMS• Natural features of Earth’s surface (including bodies of water)

• Underwater landforms are as diverse as those found on dry land• Includes flat land, mountain ranges, cliffs, valleys, and deep

trenches

• Seven large landmasses known as continents include:• Africa• Antarctica• Asia• Australia• Europe• North America• South America

• Isthmus of Panama links North and South America

• At the Sinai Peninsula, Suez canal separates Africa and Asia

• Continental shelf is an underwater extension of the coastal plain• Slopes out from land as much as 800 miles and descends to a

depth of about 660 feet

EARTH’S HEIGHTS AND DEPTHS

• Mount Everest is the highest point on Earth in South Asia• 29,028 feet above sea level

• The lowest dry land point at 1,349 feet below sea level is the shore of the Dead Sea in Southwest Asia

• Earth’s deepest known depression lies under the Pacific Ocean southwest of Guam in the Mariana Trench, a narrow underwater canyon about 35,827 feet