Plate tectonics (Midterm 1)

What is the continental drift hypothesis?

Continents move; supported by fossils, rock types, fit of continents.

What is uniformitarianism?

Present processes explain past events.

What is catastrophism?

Earth shaped by sudden, dramatic events.

What are lithospheric plates?

Rigid crust + upper mantle pieces that move on the asthenosphere.

Where are most earthquakes located?

Along plate boundaries.

Where is oceanic crust formed?

At mid-ocean ridges by upwelling magma.

What are MORB?

Basalts formed at mid-ocean ridges from partial melting of mantle.

What are magnetic stripes?

Symmetrical magnetic patterns created by seafloor spreading + magnetic reversals.

What is seafloor spreading?

New oceanic crust forms at ridges and moves outward.

Which is older: oceanic or continental crust?

Continental. Oldest rocks ~4 billion years, found on continents.

What is Pangaea?

Supercontinent that existed ~300 million years ago.

The Hawaiian chain is what type of volcanism?

Hotspot volcanism from a mantle plume; can also occur under continents.

Differences among drift, spreading, hotspot, plate tectonics?

Drift = movement of continents; spreading = creation of seafloor; hotspot = mantle plumes; plate tectonics = unified theory combining all.

What is isostatic equilibrium?

Vertical balance of crust floating on mantle; denser/thicker crust sits lower.

Major sources of Earth’s heat?

Radiogenic decay + leftover formation heat.

How does heat move to the surface?

Conduction, convection, volcanic activity.

What is a divergent boundary?

Plates move apart; new crust forms.

What is a convergent boundary?

Plates collide; three types: ocean-ocean, ocean-continent, continent-continent.

What are subduction zones?

Areas where oceanic plates sink; deep due to bending & descending slab.

When two oceanic plates converge, which subducts?

The older, denser plate.

Passive vs active margins?

Passive: no plate boundary; broad shelf. Active: plate boundary; trenches, volcanoes.

What is the Pacific Ring of Fire?

Zone of intense subduction volcanism and earthquakes around the Pacific.

How were the Himalayas formed?

Continent-continent collision between India & Eurasia.

What is a transform boundary?

Plates slide past each other.

What type of plate boundary is the San Andreas fault?

Transform boundary.