Earth Structure, Plate Tectonics, Earthquakes & Volcanoes

Fill-in-the-blank flashcards covering Earth’s structure, continental drift, plate tectonics, plate boundaries, earthquake terminology, measurement, effects and preparedness, plus volcano structure, types and impacts.

The Earth is made up of four main layers: __, mantle, outer core, inner core.

crust

The __ crust is mainly composed of granite and averages about 40–100 km thick.

continental

The oceanic crust is primarily made of __ rocks rich in ferro-magnesia.

basalt

At roughly 2,900 km thick, the __ is the thickest Earth layer.

mantle

Convection currents in the __ drive the movement of tectonic plates.

mantle

The outer core is __ (state of matter) and generates Earth’s magnetic field.

molten

Immense pressure keeps the inner core __ even at about 5,000 °C.

solid

The theory of continental drift was proposed by __.

Alfred Wegener

Wegener’s supercontinent was called __.

Pangaea

Pangaea first split into two landmasses: Laurasia in the north and __ in the south.

Gondwanaland

Matching coastlines, identical fossils, similar rock formations and __ are key evidence for continental drift.

paleomagnetism

The study of moving rigid sections of crust is called __.

plate tectonics

Earth’s crust is divided into __ major plates.

eight (8)

Plates carrying oceans are termed __ plates.

oceanic

A plate boundary where plates move apart is known as a __ (divergent) boundary.

constructive

When an oceanic plate is subducted under a continental plate, a __ (convergent) boundary is formed.

destructive

Collision of two continental plates produces __ mountains.

fold

A boundary where plates slide past one another is called a __ (transform) boundary.

conservative

Most earthquakes, volcanoes and mountain building occur at __ between plates.

boundaries

The exact point inside Earth where an earthquake starts is the __.

focus

The point directly above the focus on Earth’s surface is the __.

epicentre

Shockwaves that radiate from the focus are called __ waves.

seismic

An instrument that records earthquake vibrations is a __.

seismometer

The graphical record produced by a seismometer is a __.

seismograph

Earthquake magnitude was traditionally measured on the __ scale.

Richter

The largest recorded earthquake (1960) occurred in __ and measured 9.5.

Chile

Underwater earthquakes can generate massive sea waves known as __.

tsunamis

Rubber shock absorbers, steel frames and open assembly areas are examples of earthquake __ measures.

protection

Volcanoes usually form at constructive and __ (convergent) plate boundaries.

destructive

Molten rock stored underground beneath a volcano is called the __ chamber.

magma

Magma rises to the surface through the main __ of a volcano.

vent

The bowl-shaped opening at a volcano’s summit is the __.

crater

A steep-sided volcano built of alternating layers of lava and ash is a __ volcano.

composite (stratovolcano)

A gently sloping volcano formed by low-viscosity basaltic lava is a __ volcano.

shield

A thick, viscous mound forming near a vent is called a lava __.

dome

A volcano that has erupted in recorded history and may erupt again is classified as __.

active

Ash from eruptions can fertilise soils, which is a __ (positive/negative) impact of volcanoes.

positive

Gases, ash clouds and pyroclastic flows causing loss of life represent __ impacts of volcanoes.

negative

Geothermal energy harnessed near volcanic areas is an example of a __ (benefit/cost).

benefit

Ground shaking strong enough to damage structures is an example of a primary __ of earthquakes.

effect

In earthquake-prone regions, flexible gas connections help prevent post-quake __.

fires

Earthquakes commonly occur along the Pacific margin known as the __.

Ring of Fire

Severe earthquakes are most often associated with __ (conservative/destructive) and destructive boundaries.

conservative

Earthquakes that occur away from plate margins inside a plate are called __ earthquakes.

intraplate

Low-cost wire-mesh retrofitting and lightweight roofs help protect buildings in __ (developed/developing) countries.

developing

The shaking motion of an earthquake results from a sudden release of stored __ in rocks.

energy

In plate subduction, the denser __ plate is forced beneath the less dense continental plate.

oceanic