Earth’s Layers, Plate Tectonics, and Earthquake Mechanics

Earth's compositional layers

Crust mantle core

Earth's physical property layers

Lithosphere and asthenosphere

What is the lithosphere?

Earth's rigid outer shell broken into plates

What is the asthenosphere?

Weak plastic layer that lithosphere moves on

What does plate tectonics explain?

Most major geologic features on Earth

Why do plates move?

They interact over the weak asthenosphere

Three types of plate boundaries

Convergent divergent transform

Convergent boundary definition

Plates move toward each other

Divergent boundary definition

Plates move apart and create new crust

Transform boundary definition

Plates slide horizontally past each other

Oceanic-continental convergence results

Volcanic arcs and trenches

Oceanic-oceanic convergence results

Island arcs

Continental-continental convergence results

Large mountain ranges

Divergent boundaries on continents

Create rift valleys

Divergent boundaries in oceans

Create mid-ocean ridges and new oceanic crust

Most transform boundaries are found

On the ocean floor

Effects of active plate boundaries

Earthquakes volcanoes mountain building

Evidence of past plate interactions

Mountain belts volcanic rocks ocean crust ages

Importance of Pangaea

Supercontinent that broke apart over last 250 Ma

What causes earthquakes?

Sudden release of built-up stress along faults

Where do earthquakes occur?

Along faults where rocks slip

Primary earthquake destruction

Ground shaking

Secondary earthquake destruction

Tsunamis landslides fires subsidence

Seismic waves definition

Elastic waves that travel through Earth

Two major types of seismic waves

Body waves and surface waves

P-waves description

Fast compressional waves

S-waves description

Slower shear waves that don't travel through liquids

Types of surface waves

Love waves and Rayleigh waves

What seismograms determine?

Earthquake distance and magnitude

Purpose of triangulation

Locate earthquake epicenter

What seismic waves reveal

Earth's internal layers and properties

Three major regions of ocean floor

Continental margins deep ocean basins ocean ridges

Passive continental margin description

Wide shelf far from plate boundary

Active continental margin description

Narrow shelf at a convergent boundary

Where new oceanic crust forms

At mid-ocean ridges

Crustal deformation definition

Change in rock shape or position from stress

Three types of differential stress

Compressional tensional shear

Elastic deformation

Temporary change that returns to original shape

Ductile deformation

Permanent bending or flowing

Brittle deformation

Breaking or fracturing of rock

Fault definition

Fracture where movement occurred

Normal fault caused by

Tensional stress

Reverse fault caused by

Compressional stress

Strike-slip fault caused by

Shear stress

Folds form due to

Compressional stress

Anticline definition

Upward arching fold

Syncline definition

Downward arching fold

Factors that affect deformation

Temperature pressure stress rate

Mountain building occurs mainly at

Convergent boundaries

Oceanic-oceanic subduction creates

Island arc mountains

Oceanic-continental subduction creates

Andean-type mountains

Continental-continental collision creates

Alpine-type mountain ranges

Principle of Superposition

Oldest rock layer is at the bottom

Principle of Cross-cutting Relationships

A cutting feature is younger than what it cuts

Half-life definition

Time for half a radioactive isotope to decay

Radiometric dating determines

Absolute age of rocks

Four major eons

Hadean Archean Proterozoic Phanerozoic

Hadean Eon features

Magma ocean differentiation moon formation no life

Archean Eon features

First continents first life banded iron formations

Proterozoic Eon features

Supercontinents oxygen rise early multicellular life