Rocks

Magma

Molten rock material beneath the Earth’s crust.

Lava

Molten materials that flow onto the Earth’s surface.

Lithosphere

The outer part of the Earth, consisting of the crust and upper mantle.

Atmosphere

The layer of gases surrounding the Earth.

Rocks

Naturally-formed aggregates of minerals that make up all of the Earth’s crust and the solid part of the mantle below (Lithosphere) - building blocks of landforms

How are rocks formed?

When minerals are compacted and consolidated or pressed together to form a firm, solid substance.

• From cooling magma or lava

• From compaction of layers of rock fragments eroded from other rocks or the hardened remains of plants and animals

• From the great heat or pressure, changing the composition of the rock

Mineral

An inorganic solid with a crystalline structure and characteristic chemical composition

Igneous Rocks

Rocks formed from the cooling and solidification of molten rock (magma/lava)

Intrusive igneous rocks

Rocks formed below earth’s surface

Extrusive rocks

Formed on earth’s surface

Acid igneous rocks

Igneous rocks of high silica content (light coloured)

Basic igneous rocks

Igneous rocks of high iron and magnesium content (dark coloured)

Examples of igneous rocks

Basalt, pumice, granite

Characteristics of igneous rocks

• Coarse-grained for rocks of large crystals, vice versa

• Not in layers

• Do not have fossils

• Hard and strong (more resistant)

Sedimentary Rocks

Rocks formed from the compaction of layers of rock fragments eroded from other rocks or the hardened remains of plants and animals.

• Weathered and eroded igneous, previous sedimentary and metamorphic rock materials (clastic)

• Crystals of dissolved minerals (non-clastic)

• Organic materials such as animal and plant remains (foliated)

Conglomerate

• Sedimentary rock made up of consolidated gravels, with some mud or sand in between larger grains

• Usually form from riverbed sediments

• Large ‘cobbles’ are usually well-rounded, greater than 2 mm in diameter

Sandstone

• Sedimentary rock made from small grains of the minerals quartz and feldspar

• Form in layers

Metamorphic Rocks

Rocks formed from great heat and/or pressure beneath the Earth’s surface, changing the composition of the rock

Examples of metamorphic rocks

Marble, slate, quartzite

How to describe a rock?

• Colour

• Lustre (reflect light)

• Layering

• Crystal size

• Hardness

• Texture

Rock cycle

Weathering

The process that changes the physical and/or chemical character of rock at or near the Earth's surface.

Erosion

The picking up or physical removal of rock particles by agents such as water, wind, or ice.

Stratification

The layering that occurs in sedimentary rocks as they accumulate over time.