Unit & Plate Tectonics

Conduction

The transfer of heat through a material without the movement of the material itself.

Radiation

The transfer of energy through electromagnetic waves, such as light or heat, without requiring a medium.

Convection

The transfer of heat in a fluid (liquid or gas) where the warmer, less dense part rises and the cooler, denser part sinks, creating currents.

Thermal Conductivity

A measure of how well a material allows heat to pass through it.

Heat Transfer

The movement of thermal energy from one object or substance to another.

Insulator

A material that does not conduct heat well.

Conductor

A material that allows heat to pass through it easily.

Continental Drift

The theory that continents have moved over geological time and were once part of a single landmass.

Seafloor Spreading

The process by which new oceanic crust forms at mid-ocean ridges and spreads outwards.

Paleomagnetism

The study of Earth's past magnetic field recorded in rocks, helping to support the theory of plate tectonics and seafloor spreading.

Wegener’s Hypothesis

The idea proposed by Alfred Wegener that continents were once joined together in a supercontinent (Pangaea) and have since drifted apart.

Fossil Evidence

Similar fossils found on continents that are now widely separated.

Rock Formations

Similar rock layers and geological features across continents.

Glacial Evidence

Evidence of ancient glaciers in now-warm areas, suggesting continents were once located closer to the poles.

Fit of the Continents

The observation that continents like South America and Africa seem to fit together like a jigsaw puzzle.

Tectonic Plates

Large, rigid pieces of Earth’s lithosphere that move and interact at plate boundaries.

Divergent Boundary

Where two plates move away from each other, often causing seafloor spreading.

Convergent Boundary

Where two plates move toward each other, often causing mountain formation or subduction zones.

Transform Boundary

Where two plates slide past each other horizontally, leading to earthquakes.

Tension

Stress that stretches the material (at divergent boundaries).

Compression

Stress that squeezes the material (at convergent boundaries).

Shear

Stress that causes sliding or twisting (at transform boundaries).

Strain

The deformation or change in shape of a material due to stress.

Normal Fault

A fault where the hanging wall moves downward relative to the footwall (caused by tension).

Reverse Fault

A fault where the hanging wall moves upward relative to the footwall (caused by compression).

Strike-Slip Fault

A fault where the movement is primarily horizontal (caused by shear stress).

Lithosphere

The rigid outer layer of Earth, including the crust and upper mantle.

Asthenosphere

A semi-fluid layer beneath the lithosphere, allowing tectonic plates to move.

Seismic Waves

Waves of energy that travel through Earth’s layers due to an earthquake or other seismic event.

Primary (P) Waves

The fastest seismic waves, compressional in nature, that can travel through both solid and liquid.

Secondary (S) Waves

Seismic waves that are slower than P-waves and can only travel through solids, moving in a transverse motion.

Surface Waves

Seismic waves that travel along the Earth’s surface and are responsible for most of the damage during an earthquake.

Epicenter

The point on Earth's surface directly above the earthquake's focus (where the earthquake originates).

Focus (Hypocenter)

The point beneath Earth's surface where an earthquake originates.

Seismogram

A record of the seismic waves detected by a seismometer, used to determine the location and magnitude of an earthquake.

Seismometer

An instrument used to detect and measure seismic waves.

Triangulation

The method used to determine the epicenter of an earthquake by using data from multiple seismometer locations.

Magnitude

A measure of the energy released during an earthquake, typically measured by the Richter scale.

Intensity

A measure of the earthquake’s effects on people, buildings, and the Earth's surface, typically measured by the Mercalli scale.

Richter Scale

A scale that measures the magnitude of an earthquake, based on the amplitude of seismic waves.

Mercalli Scale

A scale that measures the intensity of an earthquake, based on observed effects on people, buildings, and the Earth's surface.