Continental Drift and Seafloor Spreading – Flashcards (Science10 notes)

A set of Question and Answer flashcards covering continental drift, seafloor spreading, plate boundaries, seismic waves, and supporting evidence from the provided notes.

Who proposed the Continental Drift Theory and in what year?

Alfred Wegener, in 1912.

What is Pangaea?

A supercontinent formed when all the continents were joined.

What ocean surrounded Pangaea and is named in the notes as Panthalassa?

The vast global ocean that surrounded Pangaea.

What is Laurasia?

The northern part of Pangaea.

What is Gondwanaland?

The southern part of Pangaea.

Name some earlier supercontinents mentioned before Pangaea.

Rodinia, Pannotia, Ur, Kenorland, Columbia/Nuna.

Was Pangaea the first supercontinent to exist according to the notes?

No; earlier supercontinents include Rodinia, Pannotia, Ur, etc.

What is Panthalassa?

The huge ocean that existed around Pangaea, meaning 'all sea'.

When did Pangaea exist according to the notes?

In the late Paleozoic to early Mesozoic eras.

What is Seafloor Spreading Theory and who proposed it?

The oceanic crust forms along mid-ocean ridges and spreads outward; proposed by Harry Hess and Robert Dietz in 1960.

What analogy is used to describe seafloor spreading?

The ocean floor moves like a conveyor belt carrying continents.

Define a divergent plate boundary.

A boundary where two plates move apart; a constructive boundary that forms rift valleys and oceanic ridges.

What forms at divergent boundaries as spreading continues?

Rift valleys in the middle, then a linear sea, and finally an oceanic ridge.

What is a mid-ocean ridge?

The world's longest chain of mountains on Earth (~65,000 km); example: Mid-Atlantic Ridge.

Define a transform boundary.

Margins where two plates grind past each other without creating or destroying lithosphere; also called conservative boundaries; example: San Andreas Fault.

What is the San Andreas Fault an example of?

A transform boundary between the Pacific and North American plates.

Name the three convergent boundary types.

Oceanic–Oceanic, Oceanic–Continental, and Continental–Continental.

What happens at Oceanic–Oceanic convergence?

Two oceanic plates converge; older one subducts, forming a trench and a volcanic island arc.

What happens at Oceanic–Continental convergence?

Denser oceanic lithosphere sinks (subduction) beneath the continental plate, forming a continental volcanic arc, trench, and earthquakes.

What happens at Continental–Continental convergence?

No subduction occurs; results in mountain building and earthquakes.

What drives plate movement according to convection currents?

Rising hot magma near the core and sinking cooler magma near the crust—mantle convection.

What is the lithosphere?

The rigid outer shell of Earth, consisting of the crust and upper mantle.

How thick is continental crust compared to oceanic crust?

Continental crust: about 25–70 km thick; Oceanic crust: about 7–10 km thick.

Which crust is denser, continental or oceanic?

Oceanic crust is denser (about 3.0 g/cm3) than continental crust (about 2.7 g/cm3).

Name the three main types of plate boundaries.

Divergent, Transform, and Convergent boundaries.

What is triangulation used for in seismology?

Using data from three seismic stations to locate an earthquake’s epicenter.

What is an epicenter?

The point on the Earth's surface directly above the focus where energy is released.

What is a P-wave?

Primary seismic wave; a compressional wave that travels through solids and liquids and arrives first.

What is an S-wave?

Secondary seismic wave; a shear (transverse) wave that travels only through solids and arrives after P-waves.

What are Love waves and Rayleigh waves?

Love waves (L-waves) are surface waves named after Love and are highly damaging; Rayleigh waves are surface waves named after Rayleigh and cause most shaking.

What evidence supports the idea of continental drift besides matching coastlines?

Fossil correlation, rock and mountain correlations, and paleoclimate data such as glacial features and coal deposits.