PLATE TECTONIC THEORY, METHODS, ABOUT EARTH

TECTONIC PLATES

several broken pieces that consist of either oceanic crust, continental crust, or both

PLATE TECTONIC THEORY

describes the structures, movements, and events that occur at each type of plate boundary

OCEANIC-CONTINENTAL CONVERGENCE

oceanic crust collides with continental crust (stuff above the water), causing trenches and mountains to form. The oceanic crust subducts underneath, heats up underneath, and makes magma rise up to the continental crust to turn some mountains into volcanoes

OCEANIC-OCEANIC CONVERGENCE

oceanic crust collides with oceanic crust, causing trenches and mountains to form (but its all underwater). The oceanic denser oceanic crust subducts underneath, heats up underneath, and makes magma rise up to the less denser oceanic crust, causing these mountains to slowly rise up from the water as volcanoes

CONTINENTAL-CONTINENTAL CONVERGENCE

continental crust collides with continental crust, causing no subduction since they are both not that dense. They collide with each other, causing them to fold/crash into each other to create mountains

DIVERGENT BOUNDARIES

when two plates move apart from each other. the plates move apart due to the magma from underneath rising up and needing space between.

TRANSFORM BOUNDARIES

when two plates move past each other. the plates move past each other horizontally, scraping against each other, which can cause earthquakes.

VELOCITY

how fast something moves and in what direction

POSITION

exact location

DISPLACEMENT

change in position

GNSS/GPS (Global Navigation Satellite System/Global Positioning System)

• receives timed signals from several satellites and calculates an exact ground position. It uses receivers that are permanently planted on the ground, while the satellites track if it moves from it’s original location.

• precise movement of installed points

InSAR (Interferometric Synthetic Aperture Radar)

• compares radar signals from satellite images taken over the same area at different times. The satellite’s view on the surface doesn’t change, which can show if anything moved away or not.

• wide-area surface deformation

VLBI (Very Long Baseline Interferometry)

• radio telescopes observe the same distant quasar and compare signal-arrival times. there are several telescopes that are fixed on a quasar. If the signal arrives later, that means that the telescopes moved away from each other.

• global telescope-to-telescope movement

Satellite Laser Ranging

• sends a laser pulse to a satellite reflector and times the returning light. If the light arrives later, that means the receiver that gave the laser pulse moved away from the satellite.

• precise ground-to-satellite distance

Seismic Monitoring

• seismometers record P waves, S waves, and surface waves from earthquakes. Earthquakes happen due to boundaries moving, so this method can help identify and prove whether the ground below is moving or not.

• sudden earthquake and fault movement

Geological Evidence

• scientists study displaced landforms, fault layers, rock ages, and magnetic patterns. They physically view the appearance or characteristics of different structures and take note of patterns that happened before.

• long-term record of past movement

COMPOSITIONAL LAYERS

what the earth is made of

CRUST

outermost, thickest layer

CONTINENTAL CRUST

thick, less dense, made of granite

OCEANIC CRUST

thin, dense, made of basalt

MANTLE

largest layer by volume, solid but flows slowly

OUTER CORE

liquid, motion creates earth’s magnetic field

INNER CORE

solid, immense pressure despite extreme heat

MECHANICAL LAYERS

how the earth behaves

LITHOSPHERE

brittle, breaks easily

ASTHENOSPHERE

semi-fluid, moving the plates

MESOSPHERE

lower mantle, transferring heat from core to other layers