Geology — Rocks, Minerals & Earth History

Feldspar

A group of rock-forming minerals that make up about 41% of the Earth's continental crust.

Basalt

A common extrusive igneous rock, usually dark-colored, formed from rapid cooling of lava.

Granite

A coarse-grained intrusive igneous rock composed mainly of quartz, feldspar, and mica.

Limestone

A sedimentary rock primarily composed of calcium carbonate (CaCO₃).

Schist

A medium-grade metamorphic rock with pronounced schistosity, derived from shale.

What is the rock cycle?

The continuous process of rock transformation from one type to another over geological time.

Erosion

The process by which soil, rock, and other surface material are removed and transported elsewhere.

Weathering

The breakdown of rocks, soils, and minerals through contact with the Earth's atmosphere, water, and biological organisms.

Plate Tectonics

The theory explaining the movement of the Earth's lithosphere which leads to seismic and volcanic activity.

What causes earthquakes?

Earthquakes are caused by the sudden release of energy in the Earth's crust due to tectonic plate movements.

Convergent Boundary

A tectonic plate boundary where two plates move toward each other, often causing mountain formation or subduction.

Divergent Boundary

A tectonic plate boundary where two plates move apart, typically resulting in seafloor spreading.

Transform Boundary

A tectonic plate boundary where two plates slide past each other horizontally, often causing earthquakes.

What is a mineral?

A naturally occurring, inorganic solid with a definite chemical composition and an ordered atomic arrangement.

Cleavage

The tendency of a mineral to break along flat, even surfaces.

Fracture

The manner in which a mineral breaks when it does not cleave along planes of weakness.

What is radiometric dating?

A method for determining the age of an object based on the decay rate of radioactive isotopes.

Fossil

The preserved remains or traces of organisms that lived in the past.

What is the significance of the fossil record?

The fossil record provides evidence of the evolution of life and the history of the Earth’s surface.

Stratigraphy

The study of rock layers (strata) and layering (stratification), crucial for understanding Earth's history.

What are silicate minerals?

Minerals that contain silicon and oxygen, and often other elements; they make up the majority of the Earth's crust.

Obsidian

A natural volcanic glass formed by the rapid cooling of viscous lava from volcanoes.

What is the principle of uniformitarianism?

The principle that the same natural laws and processes that operate in the present have always operated in the past.