Rocks- An Introduction

The Earth is dominated by rock.◦Should you dig down it is the major material that

you will encounter.

We see soil, but it is just a thin layer, like the skin of a grape or tomato.

Rocks are simply aggregates of one or more minerals.

Aggregate means a mixture

The study of rocks is the science of Petrology

Petrology

Rocks are classified into three main categories

Based on◦Origin ◦And process of creation

Main Categories of Rocks

Igneous Rocks

Sedimentary Rocks

Metamorphic Rocks

Igneous rocks

These are rocks form from the solidification of molten materials.

This materials can be either lava (on the Earth’s surface)

Or Magma (in Earth’s interior)

Sedimentary Rock

This is rock formed from the weathering and erosion of pre-existing rocks.

Metamorphic Rocks

These are rocks form from pre-existing rocks that are altered from changes in;◦Temperature,◦Pressure,◦And other environmental conditions

Rock Cycle

They may be three distinct categories of rock but they are related through the rock cycle.

The Earth is not static, but on a geological scale, the Earth is continually changing.

One rock type is being converted into another rock type.

These changes occur if the environmental conditions under which the rock formed have changed.

The rock cycle demonstrates how one rock type can become another rock type.