OCR A-Level Geology Module 3 Global tectonics overview quiz quiz

He had no supporting evidence at all for his radical proposal of drift

He could not provide a convincing mechanism to move the continents

The coastlines of the continents do not actually fit together neatly

Identical fossils were later found on every continent worldwide

Different rock types forming in alternating bands of basalt and gabbro along the ridge crest

Repeated shallow earthquakes occurring along the active mid-ocean ridge crest over millions of years

Sea-floor spreading, because crust records field reversals as it moves out equally on both sides

Subduction of cold oceanic crust pulling the magnetic minerals down into the trench

Ridge push

Tidal forces

The Coriolis effect

Slab pull

Explosive andesitic stratovolcanoes, from viscous magma generated by slab melting

Gentle basaltic shield volcanoes, built from very runny low-silica magma over time

No volcanoes form at all because the descending slab does not melt at depth

Quiet basaltic fissure eruptions only, fed directly from the upper mantle

The boundary between the crust and the mantle, marked by a velocity jump

The inclined plane of earthquake foci marking a descending subducted slab

The central rift valley running along the crest of a mid-ocean ridge

A particular type of vertical strike-slip transform fault in the ocean floor

Both colliding plates subduct rapidly and steeply down into the deep mantle, generating arc magma above each of them

The continental crust at the margin is far too thin and weak to fold, so it simply fractures into blocks

Both plates are buoyant continental crust, so neither subducts; the crust thickens and folds, with no slab to melt

Continental collisions only ever produce horizontal strike-slip faulting and never any vertical uplift

S wave

Love wave

Rayleigh wave

P wave

The energy released at the source

The effects and damage at a particular place

The depth of the focus

The number of aftershocks

It is far easier and quicker to calculate from a single seismogram trace

The Richter scale saturates and underestimates large quakes; moment magnitude does not

It measures the felt intensity and damage rather than the energy magnitude

It only works reliably for small, shallow earthquakes located near the recording station

One, because a single station records both the distance and the direction to the source

Two, because the two distance circles drawn always cross at exactly one unique point

Three, because each gives only a distance (a circle) and three circles intersect at one point

Four, with one station carefully placed in each of the four main compass directions around the focus

Only the absolute temperature of the rising magma at the moment of eruption

The colour of the erupted lava, with the darker lavas always erupting more violently

The latitude and altitude of the volcano above present-day sea level

Silica content and the resulting viscosity, which controls how easily gas escapes

The oldest rocks

The youngest rocks

Igneous rocks only

The most metamorphosed rocks

Horizontal compression

Tension (extension)

Pure shear stress only

No stress acting at all

Angular unconformity

Disconformity

Nonconformity

There is no unconformity