Physical Science Review:Physical Science Review:

Earth ScienceEarth Science

Earth’s InteriorEarth’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 TectonicsPlate 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.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 BoundariesDivergent 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 mid-ocean ridges, form at divergent plate boundaries.

• The most studied mid-ocean ridge is the Mid-Atlantic Ridge, which extends from the Artic Ocean to the southern tip of South America.

Convergent Plate BoundariesConvergent 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)

MountainsMountains

• 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 boundariesTransform 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 TectonicsEvidence 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.

EarthquakesEarthquakes

• 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.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 rock2) S waves (secondary)- transverse waves, move slower

than p waves3) Surface waves- move along Earth’s surface, cause the

most destruction

VolcanoesVolcanoes

• 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, 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 RocksMinerals 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 RocksTypes 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?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 RocksWeathering 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 AtmosphereThe 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 AtmosphereLayers 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 AtmosphereChanges 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 EffectGreenhouse 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.

WaterWater

• 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.

WindWind

• 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 ClimateWeather 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.

SeasonsSeasons

• 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