science review

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EARTH SCIENCE REVIEW – DETAILED STUDY GUIDE

1. Introduction to Earth Science

Definition:

Earth science is the study of Earth and its place in the universe. It looks at how Earth works, its materials, its processes, and how humans affect it.

Branches of Earth Science:

• Geology: Study of the solid Earth (rocks, mountains, volcanoes, earthquakes).

• Meteorology: Study of the atmosphere and weather.

• Oceanography: Study of oceans (waves, tides, currents, marine life).

• Astronomy: Study of space (stars, planets, the universe).

• Environmental Science: Study of human interactions with Earth.

Earth’s Systems:

• Geosphere: All the rock and solid Earth.

• Hydrosphere: All water on Earth (oceans, rivers, glaciers).

• Atmosphere: The gases around Earth (air).

• Biosphere: All living things.

• These spheres constantly interact (e.g., a volcano affects air and living things).

2. Rocks and Minerals

Minerals:

• A mineral is a naturally occurring, inorganic solid with a definite chemical composition and crystal structure.

• Properties for ID:

• Color

• Streak: Color of the powdered mineral

• Luster: Metallic or nonmetallic shine

• Hardness: Resistance to being scratched (Mohs scale: 1 = soft, 10 = hard)

• Cleavage: Breaks on flat surfaces

• Fracture: Breaks unevenly

Rocks:

• Made of one or more minerals.

• Rock Types:

Igneous Rocks:

• Formed from cooling magma or lava.

• Intrusive: Form underground; cool slowly = large crystals (granite).

• Extrusive: Form on surface; cool fast = small or no crystals (basalt, pumice).

Sedimentary Rocks:

• Formed from compacted sediments.

• Found in layers; may have fossils.

• Types:

• Clastic (sandstone)

• Chemical (rock salt)

• Organic (coal)

Metamorphic Rocks:

• Formed from heat and pressure changing other rocks.

• Foliated: Layered (gneiss, schist)

• Non-foliated: No layers (marble)

The Rock Cycle:

• Describes how rocks change from one type to another:

• Magma cools → Igneous

• Weathering + erosion → Sediments

• Sediments compact → Sedimentary

• Heat + pressure → Metamorphic

• Melting → Magma again

3. Plate Tectonics

Theory of Plate Tectonics:

• Earth’s crust is divided into large slabs called tectonic plates.

• Plates float on the mantle and move because of convection currents.

Evidence:

• Continents fit together (Pangaea).

• Similar fossils and rock types on opposite continents.

• Earthquakes and volcanoes at plate boundaries.

Types of Plate Boundaries:

1. Divergent: Plates move apart

• Forms mid-ocean ridges (new crust)

• Ex: Mid-Atlantic Ridge

2. Convergent: Plates move together

• Ocean + continent = subduction, volcanoes (Andes)

• Continent + continent = mountains (Himalayas)

3. Transform: Plates slide past each other

• Causes earthquakes

• Ex: San Andreas Fault

Earthquakes:

• Happen at plate boundaries.

• Measured with a seismograph (Richter scale).

Volcanoes:

• Form at divergent or convergent boundaries and hot spots.

• Lava erupts from a magma chamber.

4. Historical Geology

Geologic Time Scale:

• Earth is 4.6 billion years old.

• Time is divided into:

• Eons → Eras → Periods → Epochs

Major Eras:

• Precambrian: First life, very long

• Paleozoic: Marine life, fish, first land plants and animals

• Mesozoic: Dinosaurs, first birds

• Cenozoic: Mammals dominate, humans appear

Fossils:

• Remains of ancient life.

• Index fossils: Used to date rock layers (short-lived but widespread).

• Law of Superposition: In undisturbed layers, the oldest is at the bottom.

5. Earth’s Interior

Layers of the Earth:

• Crust:

• Thin, outer layer

• Continental crust: thick but less dense

• Oceanic crust: thin but denser

• Mantle:

• Largest layer

• Solid but flows slowly (like thick putty)

• Moves plates (convection currents)

• Outer Core:

• Liquid iron and nickel

• Creates Earth’s magnetic field

• Inner Core:

• Solid iron and nickel

• Hottest layer (pressurized)

Seismic Waves:

• Help us understand the inside of Earth.

• P-waves travel through solids and liquids.

• S-waves only go through solids.

6. Oceanography

Oceans:

• Cover 71% of Earth.

• Salty due to minerals and dissolved salts.

Ocean Features:

• Continental shelf: Shallow edge of a continent.

• Abyssal plain: Deep, flat ocean floor.

• Mid-ocean ridges: Mountains at divergent boundaries.

• Trenches: Deep areas at subduction zones.

Currents:

• Surface currents: Moved by wind (warm or cold water).

• Deep currents: Caused by temperature and salinity differences.

Tides:

• Daily rise and fall of ocean water.

• Caused by the Moon’s gravity.

• Spring tides = strongest (sun + moon aligned)

• Neap tides = weakest (sun and moon at 90°)

7. Meteorology

Atmosphere:

• Layers (from Earth upward):

1. Troposphere: Weather, clouds

2. Stratosphere: Ozone layer

3. Mesosphere: Cold, meteors burn

4. Thermosphere: Hot, auroras

Weather Tools:

• Thermometer: Temperature

• Barometer: Pressure

• Hygrometer: Humidity

• Anemometer: Wind speed

Air Pressure:

• High pressure: Cool, dry air = clear skies

• Low pressure: Warm, moist air = clouds/storms

Fronts:

• Cold front: Fast, pushes warm air up = storms

• Warm front: Slow, gentle rain

• Stationary front: Doesn’t move = long rain

• Occluded front: Cold overtakes warm = heavy rain

8. Climatology

Climate vs Weather:

• Weather: Day-to-day conditions

• Climate: Long-term average

Climate Factors:

• Latitude: Closer to equator = warmer

• Altitude: Higher = colder

• Proximity to water: Water = moderate temps

• Ocean currents: Warm/cold water affects coasts

• Topography: Mountains cause rain shadow effect

Climate Zones:

• Tropical: Hot, near equator

• Temperate: Mild

• Polar: Cold

Climate Change:

• Caused by natural cycles + human actions (greenhouse gases).

• Effects: Ice melts, rising seas, extreme weather

Here’s a detailed breakdown of the Moon, focused on what you need for Earth Science tests:

The Moon – Detailed Notes

1. Moon Phases

The Moon does not create its own light. We see it because it reflects sunlight. As the Moon orbits Earth, we see different amounts of its lit half — this causes the phases.

Cycle = about 29.5 days (a lunar month)

Phases in Order (memorize this):

1. New Moon – Moon is between Earth and Sun. We don’t see it.

2. Waxing Crescent – A sliver of light on the right.

3. First Quarter – Right half lit.

4. Waxing Gibbous – More than half, lit on right.

5. Full Moon – Earth is between Moon and Sun. Fully lit.

6. Waning Gibbous – Left side lit, shrinking.

7. Last Quarter (Third Quarter) – Left half lit.

8. Waning Crescent – Small sliver of light on the left.

9. Back to New Moon

WAXING = growing (right side lit)

WANING = shrinking (left side lit)

Crescent = less than half lit

Gibbous = more than half lit

2. Moon’s Orbit and Motion

• Orbits Earth in 27.3 days

• Rotates once every 27.3 days too, so we always see the same side (called synchronous rotation)

• Revolution (orbit) is slightly elliptical

3. Eclipses

Solar Eclipse:

• Moon blocks the Sun

• Happens during New Moon

• Order: Sun – Moon – Earth

• Moon’s shadow falls on Earth

• Can only be seen in a small area

Lunar Eclipse:

• Earth blocks sunlight to the Moon

• Happens during Full Moon

• Order: Sun – Earth – Moon

• Earth’s shadow covers the Moon

• Can be seen from anywhere it’s night

Note: Eclipses don’t happen every month because the Moon’s orbit is tilted about 5° compared to Earth’s orbit.

4. Tides

Tides are caused by the Moon’s gravity pulling on Earth’s oceans.

• 2 high tides and 2 low tides per day

• As the Moon orbits, it pulls ocean water with it, creating bulges.

Types of Tides:

• Spring Tide:

• Sun + Moon pull together (New & Full Moon)

• Highest highs, lowest lows

• Neap Tide:

• Sun + Moon pull at 90° (First & Third Quarter)

• Weak tides

5. Moon Facts

• Diameter: About ¼ of Earth’s

• Gravity: About 1/6 of Earth’s

• No atmosphere or weather

• Formed from a collision (giant impact theory)

• Surface features:

• Maria: Dark, flat areas (solid lava)

• Craters: From impacts

• Highlands: Light-colored, mountainous

You’re right! Here’s the Astronomy section—very detailed and simplified to help you for your test:

ASTRONOMY – EARTH SCIENCE REVIEW

1. What is Astronomy?

Astronomy is the study of:

• Objects in space (like stars, planets, and galaxies)

• How they move and interact

• Earth’s place in the universe

2. The Universe

• Universe: All of space and everything in it

• Galaxy: A huge group of stars; we live in the Milky Way Galaxy

• Solar System: Sun and everything that orbits it (planets, moons, comets, asteroids)

Order of the Planets (from the Sun):

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

(Tip: “My Very Educated Mother Just Served Us Nachos”)

3. Earth’s Motions

Rotation:

• Spins on axis

• Takes 24 hours

• Causes day and night

• Rotates counterclockwise (west to east)

Revolution:

• Orbits around the Sun

• Takes 365.25 days

• Causes seasons

• Earth’s orbit is slightly elliptical

4. Seasons

Seasons are caused by:

1. Earth’s tilt (23.5°)

2. Revolution around the Sun

Key Dates (Northern Hemisphere):

Season Date Sun’s Position Day Length

Spring Equinox ~March 21 Direct at Equator 12 hr day/night

Summer Solstice ~June 21 Direct at Tropic of Cancer Longest day

Fall Equinox ~Sept 21 Direct at Equator 12 hr day/night

Winter Solstice ~Dec 21 Direct at Tropic of Capricorn Shortest day

Equinox = equal day & night

5. The Sun’s Path in the Sky

• In summer, the Sun is higher in the sky; longer days

• In winter, the Sun is lower; shorter days

• The Sun rises in the east and sets in the west, but the exact spot changes with the season

6. Celestial Sphere Basics

• Zenith: The point directly above you

• Horizon: Where the sky meets the ground

• Altitude: How high an object is above the horizon (0° = horizon, 90° = zenith)

• Azimuth: Compass direction (0° = North, 90° = East, etc.)

7. Stars & Constellations

• Stars appear to move across the sky due to Earth’s rotation

• Circumpolar stars: Always visible, circle the North Star (Polaris)

• Polaris is directly above the North Pole — its altitude = your latitude in the Northern Hemisphere

• Constellations change with the seasons (caused by Earth’s revolution)

8. Earth’s Shape & Evidence

• Earth is an oblate spheroid (slightly flattened at the poles)

• Evidence:

• Photos from space

• Ships disappear bottom first

• Earth’s shadow on the Moon is curved during a lunar eclipse

• Gravity is slightly stronger at poles

9. Geocentric vs. Heliocentric Models

• Geocentric: Earth is at the center (ancient belief)

• Heliocentric: Sun is at the center (correct, by Copernicus and Galileo)

10. Gravity and Orbits

• Gravity is stronger when:

• Objects are closer

• Objects have more mass

• Planets stay in orbit due to a balance between:

• Gravity pulling them in

• Inertia (motion) keeping them moving forward