Physical Geo: Exam 1

What is geology?

The study of Earth, including its formation, composition, structure, and processes.

Why do we study Earth?

To understand natural resources, geologic hazards, Earth's formation and evolution, and how Earth's past helps us understand its future.

What is a hypothesis?

A plausible, testable explanation.

What is a scientific theory?

An explanation strongly supported by evidence and repeated testing.

What is a scientific law?

A statement or equation describing a specific relationship under certain conditions.

What are Earth's major compositional layers?

Continental crust, oceanic crust, mantle, outer core, and inner core.

What is the geocentric model?

A model with Earth at the center.

What is the heliocentric model?

A model with the Sun at the center.

Who proposed the heliocentric model?

Copernicus.

What percentage of the Solar System's mass is in the Sun?

About 99.8%.

What are the terrestrial planets?

Mercury, Venus, Earth, and Mars.

What are terrestrial planets like?

Small, rocky planets with metallic cores.

What are the Jovian planets?

Jupiter, Saturn, Uranus, and Neptune.

Which planets are gas giants?

Jupiter and Saturn.

Which planets are ice giants?

Uranus and Neptune.

What is the ecliptic?

The approximate plane in which the planets orbit the Sun.

What three criteria must an object meet to be a planet?

It must orbit a star, be roughly spherical, and clear its orbital neighborhood.

Why is Pluto not a planet?

It does not clear its orbital neighborhood.

What did Hubble's observations show?

Distant galaxies are moving away, and farther galaxies are moving away faster.

What does Hubble's observation imply?

The universe is expanding.

What is an element?

Matter that cannot be subdivided into other components with different properties.

What are the three main subatomic particles?

Protons, neutrons, and electrons.

What is nuclear fusion?

The process in which atomic nuclei combine to form larger nuclei.

What is the Big Bang theory?

The universe began in a very hot, dense state and expanded and cooled.

What elements were mainly produced during Big Bang nucleosynthesis?

Hydrogen and helium.

How do stars form?

Gravity pulls matter together, forming a protostar that can eventually begin nuclear fusion.

What is stellar nucleosynthesis?

The formation of elements inside stars through nuclear processes.

What happens when a massive star runs out of fuel?

It can collapse and explode as a supernova.

Where do elements heavier than iron form?

In processes associated with massive stars and supernovae.

What is the nebular theory?

The theory that the Solar System formed from a collapsing cloud of gas and debris.

How old is the Solar System?

About 4.6 billion years.

How did the planets form?

Material in the protoplanetary disk accumulated through collisions and gravity.

What is differentiation?

The separation of materials based on density.

What happened to dense iron during Earth's differentiation?

It sank toward Earth's center.

How did Earth's second atmosphere form?

Through volcanic outgassing.

What gases were important in Earth's second atmosphere?

Water vapor and carbon dioxide.

How did Earth's oceans form?

Earth cooled, causing water vapor to condense.

What creates Earth's magnetic field?

Movement of molten iron in the liquid outer core creates electric currents.

What are the Van Allen belts?

Regions where charged particles from the solar wind are trapped by Earth's magnetic field.

What causes auroras?

Charged particles interact with gases in Earth's atmosphere near the poles.

What is an asteroid?

A rocky body larger than about 1 meter.

What is a meteoroid?

A small piece of rock or dust up to about 1 meter.

What is a meteor?

A meteoroid entering Earth's atmosphere.

What is a meteorite?

A meteoroid that reaches Earth's surface.

What is the lithosphere?

The crust and the uppermost rigid part of the upper mantle.

What is the asthenosphere?

The weaker/plastic layer of the mantle underlying the lithosphere.

What is a tectonic plate?

A piece of lithosphere that moves as a rigid unit over the asthenosphere.

How does continental lithosphere compare with oceanic lithosphere?

Continental lithosphere is thicker and less dense; oceanic lithosphere is thinner and denser.

What moves when tectonic plates move?

Continents move as part of the tectonic plates they are attached to.

Who proposed the Continental Drift Hypothesis?

Alfred Wegener.

What was Pangaea?

The supercontinent proposed by Alfred Wegener.

What were Laurasia and Gondwana?

The northern and southern landmasses that formed as Pangaea broke apart.

What evidence supported continental drift?

Matching continents, fossils, glacial striations/deposits, climate evidence, and matching geological rock/mountain belts.

Why were matching fossils evidence for continental drift?

Identical fossils were found on continents now separated by oceans.

Why were glacial striations evidence for continental drift?

Glacial deposits and striations line up when the continents are reconstructed into Pangaea.

How did matching rock and mountain belts support continental drift?

Rock and mountain belts on separated continents match when the continents are reconstructed.

Why did coal support continental drift?

Coal indicates ancient warm, wet tropical environments, inconsistent with some continents' present locations.

What was Wegener's biggest problem?

He did not have a convincing mechanism for how continents moved.

What is bathymetry?

The measurement and mapping of seafloor depth and topography.

What is a mid-ocean ridge?

An underwater mountain system where new oceanic crust forms.

What is a trench?

A deep seafloor feature associated with subduction.

What is a seamount?

A submerged volcanic mountain that remains below sea level.

What is a volcanic island?

A volcanic mountain that rises above sea level.

What is a guyot?

A flat-topped seamount.

What is the difference between a seamount and a guyot?

A guyot is a flat-topped type of seamount.

Curvilinearly arranged volcanic islands along seafloor trenches are called:

volcanic island arcs

What is sea-floor spreading?

The process in which new oceanic crust forms at mid-ocean ridges and moves outward.

Where is the youngest oceanic crust found?

At mid-ocean ridges.

What happens to oceanic crust as it moves away from a ridge?

It becomes older and cooler.

What happens to old oceanic crust?

It is eventually destroyed by subduction.

What is paleomagnetism?

The study of Earth's past magnetic field recorded in rocks.

What is magnetic inclination?

The angle at which Earth's magnetic field enters Earth's surface.

What does magnetic inclination tell us?

The latitude where a rock formed.

What does magnetic inclination not tell us?

Longitude.

What is a magnetic reversal?

A change between normal and reversed magnetic polarity.

What is normal magnetic polarity?

Magnetic polarity in the present-day orientation.

What is reversed magnetic polarity?

Magnetic polarity opposite to the normal orientation.

What are magnetic anomalies?

Variations in Earth's magnetic field recorded by rocks.

The angular difference between magnetic north pole and geographic north pole is defined as:

magnetic declination

What are magnetic stripes?

Alternating bands of normal and reversed magnetic polarity on the seafloor.

How are magnetic stripes arranged around mid-ocean ridges?

They are parallel to the ridge and form mirror-image patterns on both sides.

Positive magnetic anomaly forms when seafloor rock has ______ polarity as the present day (normal) magnetic field.

same

Why are magnetic stripes evidence for sea-floor spreading?

New basalt forms at the ridge, records Earth's magnetic polarity, and moves outward in both directions.

What are the three types of plate boundaries?

Divergent, convergent, and transform.

What happens at a divergent boundary?

Plates move apart.

What happens at a convergent boundary?

Plates move toward each other.

What happens at a transform boundary?

Plates slide past each other.

What happens at an oceanic divergent boundary?

New oceanic lithosphere forms at a mid-ocean ridge.

What is continental rifting?

The stretching and thinning of continental lithosphere.

What can continental rifting eventually do?

Split a continent apart.

What is subduction?

When one tectonic plate sinks beneath another.

Why does oceanic lithosphere subduct?

It cools and becomes denser.

Beneath its sediment cover, oceanic crust is primarily composed of:

basalt rocks

What is a Wadati-Benioff zone?

A zone of earthquakes that traces a downgoing subducting plate.

What is slab pull?

The force caused by cold, dense oceanic lithosphere sinking into the mantle.

What type of boundary is associated with subduction?

A convergent boundary.

Mid Oceanic ridges are examples of ______ plate boundary

divergent

What happens when oceanic crust subducts beneath continental crust?

A continental volcanic arc forms.

What happens when two oceanic plates converge?

One plate subducts and a volcanic island arc can form.

What happens when two continental plates converge?

They collide and form a mountain range.