IGCSE GEOGRAPHY CHAPTER 3

Flashcards about Earthquakes and Volcanoes.

Earthquakes and volcanic eruptions

Earth's surface is constantly changing, leading to this…

Fold Mountains

Long narrow belts with parallel ridges and valleys

Flatter areas

Areas that form plateaus within mountains.

Active volcanoes

Volcanoes that have erupted in the last 80 years

Dormant Volcanoes

Volcanoes that are resting but might erupt

Extinct volcanoes

Volcanoes that will not erupt again.

Pacific Ring of Fire

Goes all the way around the rim of the Pacific Ocean, a series of narrow belts around the planet where volcanoes form.

Plates

Earth's surface is made up of a series of sections-called…

Lubricating layer

Plates move relative to each other-flowing over the hotter, more plastic rocks below that act as a…

Convectional currents

Move rigid plates between 1-10cm per year

Destructive margins

Are places where plates collide.

Subduction

The oceanic plate is forced beneath the continental plate at an angle of 45°

Ocean trenches

The deepest areas on the earth's surface, formed by the ocean floor dragged down during subduction.

Magma

Partial melting of the subducted plate and overlying mantle becomes…

Island arcs

A chain of volcanic islands.

Constructive plate margins

Are the places where a new oceanic plate is created.

Ocean ridge systems

The only constructive plate margins on earth are the…

Conservative plate margins

Plates are being conserved, not created or destroyed

Volcano

A crack in the ground which gases, lava and pyroclastic material come to the surface.

The vent

Connected to a magma chamber underground.

Volcanic vent

Largest material is dropped nearest to the…

Shield Volcanoes

Formed in oceans-at constructive plate margins, have gentle slopes, runny lava, and little ash.

Stratovolcanoes

Steeper slopes, high viscosity lava, and pyroclastic material

Craters

Circular dents usually less than 1km in diameter, formed by explosive release of a volcano

Caldera

A huge crater caused when a volcanic cone collapses into a partly empty magma chamber after a powerful eruption

Parasitic cones

A smaller cone that develops on the side of a bigger volcano, formed when the main vent becomes blocked and magma finds another outlet

Lava domes

A feature that grow on the sides of stratovolcanoes, formed from very viscous lava that can't flow far before solidifying, so the cones have steep sides.

Pyroclastic flow

Hot solid material that travels rapidly down valleys and slopes.

Mudflows(lahars)

Forms when ash mixes with water and travels down river valleys.

Mudflow barriers

Walls built across valleys to trap mudflows and protect settlements

Geothermal power

Electricity is generated from steam in a volcanically active place or by water pumped down and heated from hot rocks

Pyroclastic material

Bubbles of liquid lava burst explosively in the air then the material cools, solidifies and falls to the ground creating…

Focus

The point where the earthquake originates from.

Epicenter

The point on earth's surface directly above the focus

Mercalli Scale

A 12-point scale which assesses the effects of an earthquake

Richter scale

A scale of magnitude, which measures the total energy released by an earthquake

Tsunami

A giant wave (or series of waves) that is generated by an earthquake when there's movement in the seabed

Small earthquakes and ground deformation

Detected by seismometers and lasers.

Seismometers

Instruments that detect small earthquakes and ground deformation.

Lasers

Tools used to detect small earthquakes and ground deformation.

Viscosity

A measure of a fluid's resistance to flow; high viscosity means the substance is thick and does not flow easily.

Magma Chamber

A reservoir of magma within the Earth's crust beneath a volcano.

Ash

Fine particles of pulverized rock, minerals, and volcanic glass created during volcanic eruptions.

Oceanic Plate

A tectonic plate located under the ocean.

Continental Plate

A tectonic plate that underlies a continent.

Mantle

The layer of the Earth between the crust and the core.

Focus

The point where the earthquake originates from.

Epicenter

The point on earth's surface directly above the focus

Mercalli Scale

A 12-point scale which assesses the effects of an earthquake

Richter scale

A scale of magnitude, which measures the total energy released by an earthquake

Tsunami

A giant wave (or series of waves) that is generated by an earthquake when there's movement in the seabed

Small earthquakes and ground deformation

Detected by seismometers and lasers.