Topic 2: Rocks and Rock Cycle

• students appreciate the classification of rocks that form the earth's crust.
• students learn to identify the main characteristics of rock types.
• students understand the cyclic nature of rock formation.

New words:

Igneous rocks are non-stratified intrusions or extrusions.They can be extremely coarse-grained (granite), fine (andesite) or glassy (obsidian). They are composed of minerals that have crystallised from molten rock.

Molten rocks called magma is found under high temperatures in the Earth's interior. Some of this molten rock remains inside the Earth and some is ejected as lava onto the Earth's surface during volcanic eruptions. When the molten rock cools and solidifies, it ebcomes mineral crystals. The process of forming mineral crystals is called crystallisation. As the mineral crystals form, they join together or interlock into masses of igneous rocks

Sedimentary rocks are formed in two ways. Some are
formed by pressing together or compacting loose particles
which have been deposited on land or in water bodies such
as seas or lakes. These loose particles are called
sediments. Other sedimentary rocks are formed by the
crystallisation of dissolved minerals.

by compacting sediments

by crystalization of deposited material e.g. salt

Metamorphic rocks are sedimentary or igneous rocks that
have been altered by heat and/or pressure. As they are
derived from previously existing igneous, sedimentary or
even metamorphic rock, their appearance is variable. They
are identified by the types of minerals they contain and
their texture.

Resources: Text Book pages 352-441

Click here for Mrs. Nowlan's rock types

• Rock types (animated)
• The rock cycle (detailed diagram and explanation)
• The rock cycle (not so detailed and more understandable)
• Rock cycle experiments (excellent site for working at home or for teachers)
• Weathering and erosion (including animations)

The rock cycle