Earth's Structure: Earth's Interior, Plate Tectonics, Earthquakes, & Volcanoes

Earth's Interior

Earth's Interior

Inner to Outer: (1) inner core, (2) outer core, (3) mantle, (4) asthenosphere (upper mantle), (5) lithosphere (part of lower crust & uppermost mantle), (6) crust

crust

Earth's rigid outermost layer of rock made up of both dry land and ocean floor

mantle

dense layer made of hot, semisolid rock is located directly below the crust

outer core

the only liquid layer of the earth - a sea of mostly iron and nickel

inner core

extremely hot, solid sphere of mostly iron and nickel at the center of the earthlithosphere

lithosphere

made up of the crust and a tiny bit of the upper mantle, this layer is divided into several constantly (very slowly) moving plates of solid rock that hold the continents and oceans

asthenosphere

hot, malleable semiliquid zone in the upper mantle, directly underneath the lithosphere, on which the plates of the lithosphere move (or float)tectonics

tectonics

large-scale processes affecting the structure of Earth's crust

evidence for Plate Tectonics

puzzle fit of continents across the Atlantic Ocean supported by matching rocks, fossils, and glacial deposits on continents on opposite sides of Atlantic; corresponding rock ages and magnetic alignment of iron-rich minerals on opposite sides of the Atlantic's mid-oceanic ridge where seafloor spreading occurs

scientific hypothesis

a possible and testable answer to a scientific question or explanation of what scientists observe in nature

scientific theory

a well-tested concept that explains a wide range of observations

endogenic processes

forces within Earth that affect its surface, such as plate tectonics, volcanic eruptions, and earthquakes

exogenic processes

processes driven by the solar energy; includes weathering and erosion--the hydrologic cycle interacts with the rock cycle

orogenesis

the process of mountain building

convergent boundary

plate boundary where two plates move toward each other

divergent boundary

plate boundary where two plates move away from each other

transform boundary

plate boundary where two plates that are sliding past each other horizontally

San Andreas Fault

major geological fault in California formed by a sliding transform boundary

subduction zone

the region where an oceanic plate sinks down into the asthenosphere at a convergent boundary, usually between continental and oceanic plates

Juan de Fuca Plate

lies between the Pacific & North American plates in northwestern U.S./southwestern Canada

ocean trench

deep valley in the ocean floor that forms along a subduction zone

Marianas Trench

deepest spot in the oceans, over 35,000 feet deep, near the Philippines.

magma

molten rock beneath the Earth's surface

lava

magma that reaches Earth's surface and flows from volcanoes

volcano

vent or fissure in the Earth's surface through which magma and gases are expelled

shield volcano

large with gentle slopes of basaltic (iron-rich) lavas; common at divergent plate boundaries and oceanic hot spots; less viscous; Kilauea on the big island of Hawaii

composite volcanoes

large, steep-sided volcanoes that result from explosive eruptions of andesitic and rhyolitic (silica-rich) lava and ash along convergent boundaries; more viscous, so more explosive; also called a stratovolcano; e.g. Mt. Rainier and Mt. Fuji

cinder cones

small steep-sided volcanoes that erupt gas-rich, basaltic lavas

volcanic ash

tiny particles of pulverized volcanic rock and glass

pyroclastic flow

fast-moving avalanches of hot gas, ash, and rock

viscosity

a liquid's resistance to flowing

volcanic arc

curving chain of active volcanoes formed adjacent to a convergent plate boundaryisland arc

island arc

string of volcanoes that form as the result of subduction of one more dense oceanic plate beneath a second less dense oceanic plate.hot spot

hot spot

a volcanically active area of Earth's surface far from a tectonic plate boundary

tsunami

long high sea wave caused by an earthquake, submarine landslide, or other disturbance

Fukushima Daiichi Disaster

nuclear power plant disaster caused by a tsunami in 2011 triggered by an earthquake at the subduction zone off the east coast of Japan

sea floor spreading

process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies

mid-ocean ridge

undersea mountain chain where new ocean floor is produced; a divergent plate boundary

East African Rift Valley

valley that begins in the north with the Red Sea, extending 6,000 miles through Ethiopia to the Lake Victoria region, where it divides into eastern and western segments and continues southward

fault

a break in Earth's lithosphere where one block to rock moves toward, away from, or past another

earthquake

the vibrations in the ground that result from movement along breaks in Earth's lithosphere

strike-slip fault

a type of fault where rocks on either side move past each other sideways with little up or down motion

seismic waves

waves that originate where rocks first move along the fault

focus

the location where seismic waves originateprimary (P) waves

primary (P) waves

a type of seismic wave that involves alternating compression and expansion of the material through which it passes; these waves arrive first

epicenter

the location on the surface directly above the focus of an earthquake

secondary (S) waves

a type of seismic wave that involves moving at right angles to primary waves causing rocks to move up and down and side to side

seismograph

device that records ground movements caused by seismic waves as they move through Earth

Richter scale

scale that rates an earthquake's magnitude based on the size of its seismic waves

Mercalli scale

scale that rates earthquake's intensity based on the damage that results