Earth Science

Continental Drift Theory

Evidence that continents were once part of a single supercontinent (Pangaea)

Compositional Layers of the Earth

Crust, Mantle, Core

Crust

continental (granite, thick) & oceanic (basalt, thin)

Mantle

silicate rocks, Mg & Fe rich; convection drives plate motion.

Core

outer (liquid, generates magnetic field), inner (solid, dense)

Mechanical Layers of the Earth

Lithosphere, Asthenosphere, Mesosphere, Outer Core, Inner Core

Lithosphere

rigid, brittle, tectonic plates.

Asthenosphere

soft, ductile, allows plate movement.

Mesosphere

rigid lower mantle

Outer Core

liquid, magnetic field.

Inner Core

 solid iron & nickel.

Plate Tectonics

• Plates float on the asthenosphere.
  

• Move 2–10 cm/year.
  

Why Plates Move

Mantle Convection, Slab Pull, Ridge Push

Mantle Convection

Hot mantle material rises, cools, and sinks

Slab Pull

Cold, dense subducting plate pulls the rest of the plate

Ridge Push

Gravity pushes older crust away from elevated mid-ocean ridges

Processes at Tectonic Boundaries

• Faulting

• Subduction

• Seafloor Spreading

Faulting

Stress breaks rocks → faults → earthquakes

Subduction

One plate sinks beneath another

Seafloor Spreading

new crust forms at ridges, older crust pushed aside.

Divergent Boundaries (Constructive)

• Plates move apart → magma rises → new crust.
  
  

• Earthquakes and volcanic activity possible.
  

Oceanic–Oceanic Divergent

• Location: Ocean floor.
  
  

• Process: Oceanic crust splits, magma rises.
  
  

• Feature Formed: Mid-ocean ridge, seafloor spreading, underwater volcanoes.
  
  

• Example: Mid-Atlantic Ridge.
  

Continental–Continental Divergent

• Location: On continents.
  
  

• Process: Continental crust stretches & thins → rift valleys. Magma may rise → linear seas.
  
  

• Features Formed: Rift valleys, linear seas, eventual new ocean basins.
  
  

• Examples: East African Rift Valley, Red Sea.
  

Convergent Boundaries (Destructive)

• Plates collide → crust destroyed, deformed, or crumpled.
  
  

• Often accompanied by earthquakes, volcanoes, and mountain formation.

Oceanic–Oceanic Convergence

• One oceanic plate (older, denser) subducts under another.
  
  

• Features Formed: Deep-sea trenches, volcanic island arcs (chains of volcanoes on ocean floor).
  
  

• Examples: Mariana Trench, Aleutian Islands.
  

Oceanic–Continental Convergence

• Oceanic plate subducts beneath continental plate

• Features: Trenches, volcanic mountain ranges

• Example: Andes Mountains

Continental–Continental Convergence

• No subduction (both buoyant)

• Features: Fold mountains, plateaus

• No volcanoes

• Examples: Himalayas, Alps

Transform Boundaries (Conservative)

• Plates slide past each other

• Features: Fault lines, earthquakes

• Example: San Andreas Fault

Earth Quake Causes

• Tectonic plate movement

• Volcanic activity

• Human activities (mining, reservoirs)

Parts of an Earthquake

Focus, Epicenter, Fault

Focus (Hypocenter)

:Underground origin

Epicenter

Surface point above focus

Fault

Fracture where movement occurs

Body Waves

Travel Through the earth

P-waves

Fastest, compressional, travel through solids/liquids/gases

S-Waves

Slower, shear waves, travel through solids only

Surface Waves

Travel along the earths surface

Love waves

Horizontal motion

Rayleigh waves

Rolling motion (most destructive)

Measuring Earthquakes

Seismograph and Seismogram

Weather

Short-term atmospheric conditions

Climate

Average weather over ~30 years

Factors Affecting Climate

Latitude, altitude, ocean currents, winds, topography

Latitude

Latitude is the distance of a place from the Equator.

Altitude

Height Above Sea Level

Distance from the Sea

Seas heat and cool slowly, while land heats and cools quickly.

Ocean Currents

Ocean currents are streams of warm or cold water in oceans.

Prevailing Winds

• Winds carry heat and moisture.

• Winds from oceans bring rainfall.

• Winds from land are usually dry.

Elements of Weather

Temperature, humidity, precipitation, wind, air pressure

Temperature

Measures how hot or cold the air is.

Humidity

Refers to the amount of water vapor (moisture) in the air.

Precipitation

Any form of water falling from the sky.

Wind

The movement of air from high pressure to low pressure areas.

Atmospheric Pressure

The weight of air pressing down on the Earth.

Climate Types

Tropical, Dry, Temperate, Continental, Polar

Troposphere

Lowest layer

Weather occurs here

Stratosphere

Temp increases

Ozone layer, planes

mesosphere

Coldest layer

Meteors burn up

Thermosphere

Hottest layer

Ionosphere

Exosphere

Outermost

Satellites orbit

Igneous

Magma/lava (Granite, Basalt)

Sedimentary

Sediments (Sandstone, Limestone)

Metamorphic

Heat & pressure (Marble, Slate)

Weathering

rocess by which rocks are broken down at Earth’s surface into smaller pieces or new substances.

Physical Weathering

is the breaking of rocks into smaller pieces without changing their chemical composition.

Chemical Weathering

the process where rocks are chemically changed into new substances due to chemical reactions.

Planets

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

Moon Phases

New → Waxing Crescent → First Quarter → Waxing Gibbous → Full → Waning Gibbous → Third Quarter → Waning Crescent

Solar Eclipse

New Moon

Lunar Eclipse

Full Moon

Tides

• Caused by Moon & Sun’s gravity

• Spring Tide

• Strongest (aligned)

• Neap Tide

• Weakest (right angles)