Transcript PS review Earth

Physical Science Review:
Earth Science
Earth’s Interior
• The layers of the Earth are the crust, the
mantle, and the core.
• Crust- top layer, made up of solid rock
Oceanic crust- beneath oceans, about
2.5-4.3 miles thick
Continental crust- less dense but thicker
than oceanic crust, about 12-25 mi. thick
Abundance of Elements in Earth’s Crust
• Mantle- layer of rock beneath the crust,
about 1800 mi. thick. Makes up 80% of
Earth’s volume. Outer mantle is solid, but
inner mantle is hot and pliable.
• Core- Composed mainly of iron and
nickel. Inner core is solid metal, outer
core is liquid metal.
• Earth’s interior gets warmer with depth.
Contains radioactive isotopes.
Plate Tectonics
• Continents may have at one time been one
supercontinent called Pangaea. The
mechanism by which the continents moved
apart was continental drift.
• Plate tectonics- theory that Earth’s surface
is made up of large moving plates.
Plate tectonics, cont.
• Lithosphere- the thin outer shell of the
Earth consisting of the crust and rigid
upper mantle.
• Beneath the lithosphere is the
asthenosphere, consisting of slow-flowing
molten rock.
• Plates of the lithosphere “float” on top of
the asthenosphere due to convection
currents.
Divergent Plate Boundaries
• A divergent boundary occurs where two plates
move apart, creating a gap. Magma rises from
the asthenosphere and cools to form new
lithospheric rock.
• Rift valleys and mountain systems, such as midocean ridges, form at divergent plate
boundaries.
• The most studied mid-ocean ridge is the MidAtlantic Ridge, which extends from the Artic
Ocean to the southern tip of South America.
Convergent Plate Boundaries
• Convergent plate boundaries are sites where
oceanic plates slide beneath oceanic or
continental plates and into the asthenosphere.
• Ocean trenches, mountains, and volcanoes are
formed at these subduction zones.
• The deepest ocean trench is the Mariana Trench
in the Pacific Ocean off the coast of Asia (6.8 mi.
deep)
Mountains
• Mountains can form at the boundary
between oceanic crust and continental
crust. Oceanic plate melts, rising magma
pushes up crust above it forming a
mountain.
• Example: Andes Mountains
• Collision of continental plates also can
form mountains. Example: Himalayas
Transform fault boundaries
• Fault- crack in the lithosphere where rocks
move past one another.
• Transform faults occur where plates move
horizontally past each other at faults along
plate boundaries.
• Earthquakes often result from this plate
movement.
• Example: San Andreas fault
Evidence for Plate Tectonics
• The alignment of iron minerals in oceanic
rocks supports the theory of plate
tectonics.
• Rocks at the center of a ridge are younger,
and get older moving away from the ridge.
• This suggests that the crust was moving
away from the plate boundary.
Earthquakes
• Earthquakes result from sudden movement
within the Earth’s lithosphere. As plates move,
rocks along the edge experience immense
pressure and break along a fault line.
• Energy is released as vibrations or seismic
waves.
• Seismology is the study of earthquakes.
• The Richter scale measures the magnitude of
earthquakes
Earthquakes, cont.
• Focus- point where rocks first break, origin of the
earthquake
• Epicenter- point on Earth’s surface immediately
above the focus.
• Earthquakes generate three types of waves:
1) P waves (primary)- longitudinal waves, move fastest
through rock
2) S waves (secondary)- transverse waves, move slower
than p waves
3) Surface waves- move along Earth’s surface, cause the
most destruction
Volcanoes
• Volcanoes are openings (vents) in Earth’s crust
where magma has reached the surface.
• Types of volcanoes:
1) Shield- gently sloping mountain formed by mild, frequent
eruptions releasing fluid lava. Ex) Mauna Loa, HI
2) Composite- steep-sloped volcano made of alternating
layers of ash, cinders, and lava Ex) Mt. Fuji, Japan
3) Cinder cone- smallest and most abundant, formed by
violent eruptions releasing ash and lava. Active for a
short time, then dormant Ex) Paricutin, Mexico
Volcanoes, cont.
• Volcanoes forming underwater are called
seamounts.
• Volcanoes occur at convergent plate
boundaries. 75% of active volcanoes are
located along the edge of the Pacific Ocean
where oceanic plates collide with continental
plates. “Ring of Fire”
• Volcanoes can also form at divergent plate
boundaries. When plates diverge, magma fills
the gap and creates volcanic mountains. Ex)
Iceland on the Mid-Atlantic ridge is a volcanic
island
Minerals and Rocks
• Minerals are nonliving substances found in
the Earth that have a definite chemical
composition and structure.
• Rocks are made up of minerals.
• The three categories of rocks include:
Igneous, Sedimentary, and Metamorphic.
• Rocks are continually broken down and
reformed by a process called the Rock
Cycle.
Types of Rocks
• Igneous- rock formed from cooled and hardened
magma (lava).
1)Extrinisic- cools on Earth’s surface ex) obsidian
2)Intrinsic- cools beneath Earth’s surface ex) granite
• Sedimentary- formed from compressed deposits
of sediments Ex) sandstone
• Metamorphic- formed from other rocks as a
result of heat, pressure, or chemical processes.
Ex) marble
How Old Are Rocks?
• Principle of Superposition- Assuming no
change in the position of rock layers, the
oldest will be on the bottom and the
youngest on top. Gives relative age of
rocks.
• Radioactive dating can give the absolute
age of rocks.
Weathering of Rocks
• Physical weathering breaks down rocks by
water erosion, ice wedging, plant root
wedging, wind abrasion, and other
physical forces.
• Chemical weathering occurs when
minerals in the rock react chemically and
break down, such as in the presence of
acid rain.
The Atmosphere
• The atmosphere is a layer of gases
surrounding the Earth.
• The main gases in the atmosphere are
nitrogen (78%) and oxygen (21%) and
other gases in trace amounts.
• The atmosphere shields living things from
harmful UV radiation, and helps maintain
surface temperatures suitable for life.
Layers of the Atmosphere
• Troposphere- dense layer closest to
Earth’s surface where weather occurs,
temp. decreases with altitude
• Stratosphere- contains the ozone layer
which protects against UV rays, temp.
increases with altitude.
• Mesosphere- coldest layer
• Thermosphere- temp. increases with
altitude
Changes in Earth’s Atmosphere
• Photosynthetic organisms add O2 to the
atmosphere.
• Animals release CO2 into the atmosphere
through cellular respiration.
• Burning fossil fuels releases large
amounts of carbon dioxide, which may
lead to global warming.
• Manmade chemical released into the air
are depleting the ozone layer.
Greenhouse Effect
• The greenhouse effect keeps the Earth
warm.
• Greenhouse gases such as water vapor
and carbon dioxide absorb energy from
the sun, which warms the troposphere.
• Global warming results when too much
heat is trapped, which could cause polar
ice caps to melt, ocean levels to rise, and
droughts to occur in some places.
Water
• Water is continually moved through the
troposphere by the water cycle.
• Water from oceans and lakes evaporates
and rises in the atmosphere. After it cools
and condenses, the water falls back to
Earth as precipitation.
• Humidity is the amount of water vapor in
the atmosphere.
• Warm air can hold more moisture than
cooler air.
• Clouds form as warm, moist air rises.
• Clouds are classified according to their
appearance and the altitude at which they
occur.
Wind
• Wind is caused by differences in air pressure.
• The air in a pressure gradient moves from areas
of high pressure to areas of low pressure.
• Earth’s rotation affects the direction of winds.
This is the Coriolis effect.
• Winds in the Northern Hemisphere curve right,
while winds in the Southern Hemisphere curve
left.
Weather and Climate
• Weather refers to the atmospheric conditions at
a certain location at a given time.
• Climate refers to weather patterns occurring
over an extended period of time.
• Climate is influenced by latitude, topography
(landforms), air circulation, and ocean currents.
• Coastal areas tend to have warmer climates
than inland areas due to warm ocean air.
• A warm front forms as a warm air mass
moves over a slower cold air mass.
• A cold front forms as a cold air mass
moves under a slower warm air mass.
• Tornadoes are high-speed rotating winds
that form as air begins to rotate around
quickly rising warm air.
• Hurricanes are large storm systems that
are characterized by high-speed winds
and very low pressures.
Seasons
• Earth’s tilt on its axis as it revolves
around the Sun causes the seasons.
• Summer occurs in the Northern
Hemisphere when the North Pole is tilted
toward the Sun.
• The summer solstice is the longest day
of the year, around June 21.
• When the North Pole is tilted away
from the Sun, it is winter.
• The winter solstice, the day with the
shortest period of daylight, occurs
around December 21.
• The spring equinox (Mar. 21) and
autumn equinox (Sept. 22) are days
when daylight and dark are equal.
The Seasons