Earthquakes and Tectonic Plates

• Earthquakes involve tectonic plates
• Tectonic plates are massive, irregularly shaped slabs of solid rock

Types of Tectonic Plates

• Continental plates are older and more dense
• Oceanic plates are newer and less dense

Tectonic Plate Boundaries

• Tectonic plate boundaries are zones where two tectonic plates meet

Types of Boundaries

• Transform boundaries involve plates sliding past each other
• Divergent boundaries involve plates moving apart
• Convergent boundaries involve plates colliding
• Subduction zones are areas where two tectonic plates meet, and one is forced beneath the other

Tension

• Tension occurs when divergent plates pull apart, stressing the rock and thinning it
• Compression is the most common stress at convergent plate boundaries
• Tension is the major type of stress at divergent plate boundaries
• Shear involves parallel forces moving in opposite directions, causing rocks to break

Anatomy of an Earthquake

• The focus is the place within Earth where the first motion occurs
• The epicenter is the place on Earth's surface above the focus
• Seismic waves are energy released at the focus, causing waves to travel outward
• Fault trace is the intersection of a geological fault with the ground surface

Types of Faults

• Normal fault is the most common type, with dip-slip faults and the hanging wall moving downward
• Strike-slip fault occurs when blocks of rock slide past one another horizontally
• Reverse thrust fault has the hanging wall moving upward, relative to the block of rocks below

Causes and Types of Stress

• Stress is the force applied to an object
• Compression squeezes rocks together, causing them to fold or fracture
• Rocks under tension lengthen or break apart

Force and Motion

• Force is a push or pull that makes an object move, stop, or change direction

Types of Forces

• Gravity pulls objects toward the Earth, preventing them from floating away
• Friction slows down or stops objects when they rub against each other
• Normal force pushes up from a surface
• Applied force is directly applied to an object, like pushing a box
• Tension is a pulling force in ropes, cables, or strings
• Air resistance slows down objects moving through the air

Types of Motion

• Linear motion involves moving in a straight line
• Rotational motion involves spinning around a point
• Periodic motion involves repeating motion

Earth's Atmosphere

• The atmosphere is the layer of air that surrounds Earth, keeping the Earth warm, providing oxygen, and protecting it from the Sun's harmful rays
• There are five main layers to Earth's atmosphere

Layers of the Atmosphere

• Troposphere (0-12 km) is where we live, and all weather happens; it gets colder as you go higher
• Stratosphere (12-50 km) is where planes fly because the air is calmer, and the ozone layer protects from the Sun's UV rays; it gets warmer as you go higher because ozone absorbs sunlight
• Mesosphere (50-80 km) is where meteors burn up, creating shooting stars; it's the coldest layer, and it gets colder as you go higher
• Thermosphere (80-700 km) is very hot, and the Northern and Southern Lights (auroras) happen here; the International Space Station (ISS) orbits here; it gets hotter as you go higher
• Exosphere (700-190,000 km) is the last layer before space, with super thin air, and satellites orbit here

Ozone Layer

• Ozone Layer (20-30 km) is a shield in the stratosphere that blocks harmful Sun rays

Other Important Parts

• Exobase (700-1,000 km) is the place where air is so thin that it starts fading into space
• Kármán Line (100 km) is the line where Earth's atmosphere officially ends, and space begins