Geology Vocab

Hot spot volcano

Hot spot volcano

An area of the earth's mantle in which the formation of a plume takes place and rises upwards. This creates a volcano on the overlying crust.

Convection current

Cycle of movement that causes heated molecules to rise and cool molecules to fall.

Crust

Layer of the earth that is the thinnest and coldest. Outermost layer.

Mantle

Layer of earth that is the thickest.

Outer core

Layer of earth that surrounds the inner core.

Inner core

The hottest layer of earth and the innermost.

Magma

Hot fluid or semi-fluid material below or within the earths crust from which lava and other igneous rock is formed on cooling.

Lava

Hot molten or semi-fluid rock erupted from a volcano or fissure, or solid rock resulting from cooling of this.

Lava Fields

Once the volcanic explosion has happened and basaltic lava is flowing down from the crater, the lava fields begin to form. The rocks that are an outcome of this phenomenon are jagged and sharp, with the color being a deep grey.

Scoria cone

The scoria rocks fall in piles all around the crater of Rangitoto, creating a cone shaped formation. These rocks are a muddy reddish brown due to the lava cooling and becoming solidified rock.

Lava caves

The lava caves in Rangitoto are hollow openings underneath the surface of the island. These caves are full of rocks and are exposed due to weathering.

Moat

The moat is a dipped shape found in the north, south, and middle points of the top of Rangitoto. A result of hot magma cooling and forcing the mountain to subside.

Scoria rock

Dark colored igneous rock which forms because of lava rapidly cooling. This is why there are many air pockets inside because there was no time for air to escape.

Basalt rock

Dark colored igneous rocks which form because of lava slowly cooling. There are no air pockets inside due to the air escaping before the rock is fully cooled.

Silica

A substance contained in volcanic rocks. What gives the rock its glass like texture. The more silica, the higher viscous.

Viscosity

The method of measuring the thickness and resistance (how well it flows)

High viscosity: Thick, does not flow well. High viscous. High resistance to flow.

Low viscosity: Flows easily, runny. Low viscous. Low resistance to flow.

Weathering

weathering is the process of gradually breaking rock over time.

Primary succession

the gradual creation of an eco-system that inherently came from nothing but bare rocks.