Download Unit One: The World

Unit 2: Physical Geography
The Universe
► Earth
is a part of a larger physical system that
contains other planets, moons, and stars. This
system is called the Universe. The Universe
contains billions of galaxies, each with billions of
stars. Many stars have their own system of
planets, moons, and other orbital bodies.
► Our
galaxy is called the Milky Way. Earth is part
of a solar system within the Milky Way. Our solar
system revolves around our star, the Sun.
Our Solar System
► Our
solar system is made up of the Sun and
other objects that revolve around it.
The Sun
► Stars
are giant balls of
burning gases. Our
Sun is a medium-sized
star. Its enormous
mass creates a strong
gravitational pull which
keeps the earth and
other objects revolving
around it.
The Planets
► Planets—There
are eight planets that revolve
around the Sun. The inner planets are Mercury,
Venus, Earth, and Mars. These are the terrestrial
planets. The outer planets are Jupiter, Saturn,
Uranus, and Neptune. These are called gas
giants.
► Moons—Planets
have natural satellites called
moons. We have one moon. Jupiter has the most
with 63. Not all moons are like ours. Some have
atmospheres. Others are irregular in shape,
similar to asteroids.
►
Dwarf Planets—Small round bodies that orbit
the Sun but have not cleared their orbits of
other bodies are called dwarf planets. The
largest dwarf planets are Pluto, whose orbit is
beyond Neptune, and Ceres, whose orbit lies
between Mars and Jupiter.
►
Asteroids, Comets and Meteoroids
 Asteroids—small irregularly shaped planet-like
objects; most are found in the asteroid belt
between Mars and Jupiter
 Comets—icy dust particles & frozen gases with
long feathery tails; they have irregular orbits
which cross planetary orbits
 Meteoroids—chunks of rock and iron; some
enter Earth’s atmosphere; those that impact the
Earth are called meteorites; mostly insignificant,
though some have caused catastrophic damage
Earth
► The
Earth is a rounded object, wider when
measured at the Equator than from pole to pole.
The Earth’s diameter is 7,930 miles, and its
circumference is 24,900 miles.
► Earth
is the largest of the inner planets.
► The
Earth is composed of:
 Water—about 70% of the Earth’s surface is
covered by water—oceans, lakes, rivers, and
other bodies of water.
 Land—about 30% of the Earth’s surface is land.
 Air—the layer of gases above Earth’s surface is
made up of nitrogen (78%), oxygen (21%), and
other gases
 All life exists on or near the surface of the
Earth.
► Landforms—different
shapes and elevations of
land and undersea surfaces make up Earth’s
landforms. Some are directly connected above
water, others stand alone as islands.
► From
the shore, the land extends out from the
coastal plain to form the continental shelf. This
leads to the continental slope, which is a sharp
drop-off of the continental shelf. This in turn
leads to the ocean floor.
Continental Shelf, Slope, and Ocean Floor
Landforms
► Some
common examples of landforms are:
 mountain
 valley
 river
 cape
 bay
 gulf
Name ten other types of landforms.
Earth’s Extreme Landforms
 Mount Everest is the Earth’s tallest peak,
standing 29,028 feet above sea level.
 The shore of the Dead Sea lies 1,349 feet below
sea level, making it the lowest area of dry land
on the planet.
 At 35,827 feet below sea level, the Mariana
Trench is the deepest spot on the globe.
Earth’s Structure
► Core—made
of iron and nickel the solid
inner core is surrounded by an outer liquid
core. The core is under enormous pressure.
► Mantle—thick
► Crust—rocky
layer of hot, dense rock
shell that forms the Earth’s
surface. It ranges from 2 to 75 miles thick
and is composed of more than a dozen
movable plates.
Seismic Activity
Seismic activity—earthquakes and volcanic
eruptions—happens everyday.
Recent Seismic Activity
Tectonic Plates
► The
earth’s surface is composed of about a
dozen tectonic plates that are in motion
against each other. Over millions of years,
their movement has produced the landforms
and bodies of water that we know today.
Plate Movement
► Continental
drift—theory that the continents were
once joined and have slowly drifted apart
► Plate
tectonics—physical processes that have
created many of the Earth’s physical features.
Plates are constantly moving and, over millions of
years, form mountains, create volcanoes, and
produce earthquakes.
► Magma—molten
rock. Magma is pushed up from
the mantle when plates separate.
Plates
► Subduction—occurs
when a heavier sea plate
collides with a continental plate and is thrust
downward. Then magma bursts through and
creates volcanic mountains.
► Accretion—occurs
when a continental plate slides
over a sea plate, leveling underwater features and
expanding the continental land mass.
► Spreading—occurs
when sea plates pull apart and
magma flows upward creating undersea volcanic
mountains, ridges, and sometimes islands.
Folds and Faults
► Folds—occur
when plates push against each
other and cause the Earth’s surface to
buckle. This process causes folds, or bends,
in layers of rock.
► Faults—created
when plates slide or grind
past each other causing cracks in the
Earth’s surface.
► Earthquakes—sudden
and violent
movements of tectonic plates along a fault
line.
► Volcanic
eruptions—periodic expulsion of
magma between plates, causing eruptions
of gas, ash, and lava.
External Forces of Change
► Weathering—breaking
down rocks
 Physical erosion—large rock masses are broken
down by physical actions
 Chemical erosion—large rock masses are broken
down by chemical changes in their composition
► Erosion—wearing
away the Earth’s surface
 Wind erosion—movement of dust, sand, and
soil from one place to another
 Glacial erosion—movement of rocks and soil by
the slow, gradual changes in glaciers
 Water erosion—continual movement of soil and
rocks by water slowly erodes surfaces,
creating/modifying valleys, canyons, shorelines
Earth’s Water
► Earth’s
water resources are constant—the
amount of water on our planet does not
change.
► Water
cycle—the regular movement of
water from ocean to air to land and finally
back to ocean
► Evaporation—the
changing of liquid water
into vapor, or gas, by the sun’s energy
► Condensation—liquid
water vapor cools
water created when
► Precipitation—moisture
such as rain, sleet,
or snow released from clouds
Bodies of Water
► Salt
water
 Oceans—about 97% of the Earth’s water is salt
water found in oceans, seas, and gulfs
 Five principal oceans
►Pacific
(largest)
►Atlantic
►Indian
►Arctic
►Southern
► Freshwater
 Rivers, lakes & streams—about 3% of our
planet’s water supply is freshwater; more than
2% is locked in ice. Less than 1% of Earth’s
water is found in lakes, rivers and streams.
 Groundwater—freshwater that lies beneath the
Earth’s surface
 Aquifer—a porous underground layer of rock
saturated by very slow flows of water