Earth Science: Plate Tectonics, Geology, Oceans & Astronomy

Who proposed continental drift in 1915?

Alfred Wegener.

What was Pangaea?

A supercontinent that began breaking apart about 200 million years ago.

How are lithosphere and asthenosphere different?

Lithosphere is rigid plate-bearing outer shell; asthenosphere beneath permits plate movement.

What is slab pull?

Descending oceanic lithosphere pulls the rest of the plate.

What happens at divergent boundaries?

Plates move apart, creating rifting/seafloor spreading and new crust.

What occurs at ocean-continent convergence?

Ocean crust subducts; trenches, continental volcanic arcs and mountains can form.

What is a transform boundary?

Plates slide horizontally past each other.

What supports seafloor spreading?

Ocean-floor sediment ages/thickness and magnetic reversals recorded in crust.

What causes an earthquake?

Rapid release of energy as rocks move along faults (elastic rebound).

What is the focus of an earthquake?

The underground location where earthquake waves originate.

What is the epicenter of an earthquake?

The point on the surface directly above the focus.

How is an epicenter located?

Use P-S arrival-time differences at three seismic stations and intersect distance circles.

What is the difference between a seismograph and a seismogram?

Seismograph is the instrument; seismogram is its recorded trace.

What happens for a +1 Richter magnitude increase?

10 times the wave amplitude and roughly 32 times the energy.

What is the difference between magnitude and intensity?

Magnitude measures earthquake size; intensity describes shaking/damage at a location.

What is liquefaction?

Water-saturated sediment temporarily loses strength and behaves like a fluid.

Define magma viscosity.

Resistance of magma to flow.

What raises magma viscosity?

Higher silica content and generally lower temperature.

Why can gas-rich viscous magma erupt explosively?

Gases cannot escape easily, causing pressure buildup.

What is a caldera?

Large summit depression, identified in slides as more than 1 km wide.

What are fumaroles?

Secondary vents that emit volcanic gas.

What is a pyroclastic flow (nuée ardente)?

A hot, fast-moving mixture of ash and gases down a volcano.

What is a lahar?

A volcanic mudflow.

What is the difference between blocks and volcanic bombs?

Blocks are ejected solid pieces; bombs are ejected while hot/molten.

What is the difference between concordant and discordant intrusion?

Concordant runs parallel to host-rock layers; discordant cuts across them.

What is the difference between brittle and ductile deformation?

Brittle rocks fracture; ductile rocks change shape without breaking.

Name the three types of stresses.

Compression (squeezing), tension (pulling), shear (sliding).

What is the difference between anticline and syncline?

Anticline is an upward arch; syncline is a downward trough.

What is the oldest rock layer in a dome?

The oldest rock layers.

What is the youngest rock layer in a basin?

The youngest rock layers.

What is a hanging wall?

Rock above a dipping fault surface.

What does dip measure?

Steepest downward angle of a planar rock surface from horizontal.

What is isostatic adjustment?

Crust uplifts or subsides to regain gravitational balance after a load changes.

What is the difference between relative and absolute dating?

Relative dating orders events; absolute dating estimates numerical age.

What is superposition?

Undisturbed sedimentary beds are older at bottom and younger at top.

What is cross-cutting?

A feature that cuts another rock unit is younger than the unit cut.

What is original horizontality?

Sedimentary layers were initially laid down approximately horizontally.

What is an angular unconformity?

Tilted older beds underlie younger, more horizontal beds.

What is a disconformity?

A missing interval between parallel sedimentary layers.

What is a nonconformity?

Sedimentary layers lie on eroded igneous or metamorphic rock.

What makes an index fossil useful?

It was geographically widespread but lived for a short geologic time.

What is the half-life of carbon-14?

5,730 years.

What is chemical differentiation?

Dense metals sank into Earth's core while lighter rock formed mantle and crust.

What is outgassing?

Release of interior gases, especially by volcanoes, to form early atmosphere.

What organisms first added significant oxygen?

Photosynthesizing bacteria, including cyanobacteria.

List geologic time units from largest to smallest.

Eon, era, period, epoch.

Order Phanerozoic eras from oldest to youngest.

Paleozoic, Mesozoic, Cenozoic.

What happened at the end of the Paleozoic?

The large end-Permian mass extinction.

Which era is known as the age of dinosaurs?

Mesozoic.

Which era is known as the age of mammals?

Cenozoic.

What is a craton shield?

The exposed part of an ancient stable continental core.

What percent of Earth's surface is covered by oceans?

Approximately 71%.

What is bathymetry?

Measurement and mapping of ocean depths and seafloor shape.

Name three major ocean-floor topographic units.

Continental margin, ocean basin floor, mid-ocean ridge.

What is the difference between shelf, slope, and rise?

Shelf is gently sloping submerged continent; slope descends steeply; rise is sediment apron at base.

What is a turbidity current?

Downslope flow of dense sediment-laden water.

What are abyssal plains?

Very level, sediment-covered deep-ocean areas.

What is a guyot?

A flat-topped underwater volcanic mountain.

Name three ocean-sediment types.

Terrigenous, biogenous and hydrogenous.

What is the difference between fringing reef, barrier reef, and atoll?

Fringing attaches to coast; barrier offshore with lagoon; atoll ring surrounds lagoon.

What is a light-year?

A distance traveled by light in one year; slides approximate 6 trillion miles.

What does galactic redshift indicate?

A galaxy is moving away from the observer.

Why do massive stars end differently than smaller stars?

Massive stars can undergo supernovae, producing neutron stars or black holes.

What type of galaxy is the Milky Way?

Barred spiral.

What happens to photon energy as wavelength decreases?

Energy increases.

Who developed the geocentric model?

Ptolemy.

State Kepler's first law.

Planets move in elliptical orbits around the Sun.

What is the difference between solar and lunar eclipse?

Solar: Moon blocks Sun at new Moon. Lunar: Earth's shadow falls on Moon at full Moon.

Name the terrestrial planets.

Mercury, Venus, Earth, Mars.

Name the Jovian planets.

Jupiter, Saturn, Uranus, Neptune.

Where do short- and long-period comets originate?

Kuiper belt (short) and Oort cloud (long).