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

Rocks are classified into three main
categories
 Based on
◦ Origin
◦ And process of creation
Petrology

Igneous Rocks

Sedimentary Rocks

Metamorphic Rocks
Main Categories of 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)
Igneous rocks

This is rock formed from the weathering
and erosion of pre-existing rocks.
Sedimentary Rock

These are rocks form from pre-existing
rocks that are altered from changes in;
◦ Temperature,
◦ Pressure,
◦ And other environmental conditions
Metamorphic Rocks

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.
Rock Cycle

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.