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Rocks by Mind Map: Rocks

1. Main Types of Rocks

1.1. Igneous

1.1.1. Forms when lava from a volcanic eruption cools and hardens on the Earth's surface / Forms when sedimentary and metamorphic rocks melt at convergent plate boundaries to form magma which escapes to Earth's surface to form igneous rocks.

1.1.2. Characteristics:

1.1.2.1. Hard & Strong

1.1.2.2. Crystalline Appearance

1.1.3. A few examples of igneous rocks: Granite, Basalt, Obsidian.

1.1.3.1. Granite - Coarse grain, magma cools slowly and hardens in the crust. Hence, crystals have time to grow.

1.1.3.2. Basalt - Fine grain, magma cools quickly and hardens in the Earth's surface. Hence, crystals have no time to grow.

1.1.3.3. Obsidian - Cools and hardens extremely quickly, hence crystals have no time to form at all.

1.2. Sedimentary

1.2.1. Weathering and erosion break rocks down into sediments which are transported and deposited. Sediments may be piled up on one another and the weight of the layers compress and compact the sediments together. These sediments are cemented together to form a sedimentary rock.

1.2.2. Characteristics:

1.2.2.1. Most of them have a layered appearance.

1.2.2.2. Plant and animal fossils can be found in many sedimentary rocks.

1.2.3. A few examples of sedimentary rocks: Sandstone, Shale, Conglomerate, Limestone.

1.2.3.1. Sandstone - Very fine grain.

1.2.3.2. Shale - Made from clay-sized mineral particles

1.2.3.3. Conglomerate - A mixture of pebbles and sand cemented together.

1.2.3.4. Limestone - Not formed from sediments but from the remains of coral, shells, and bone. Fossils can be found in it.

1.3. Metamorphic

1.3.1. Sedimentary or igneous rocks that have been transformed under intense pressure and heat.

1.3.2. Usually occurs at plate boundaries.

1.3.3. A few examples of transformation of rocks:

1.3.3.1. Granite --> Gneiss

1.3.3.2. Limestone --> Marble

1.3.4. Characteristics:

1.3.4.1. Hard & Strong

1.3.4.2. Crystalline appearance as under intense heat and pressure, the minerals of the original rocks recrystallise, forming large crystals in coarse-grained rocks.

1.3.4.3. Banded structure known as foliation as high pressure causes the minerals of the original rock to rearrange into bands.

2. What are rocks?

2.1. Solid material of the Earth's crust.

2.2. Made up of minerals. (e.g. quartz, silica)

2.3. Can be classified according to how they are formed: Igneous, Sedimentary, Metamorphic.

3. Characteristics that rocks can be grouped according to:

3.1. Colours

3.2. Hardness (If it can be scraped)

3.3. Grain-size (Coarse grain or Fine grain)

3.4. Appearance (Layering, Banding, Crystalline)

4. Tems

4.1. Erosion - The wearing away of the land surface by various natural agents, the most important bieng water.

4.2. Rock - One of the solid materials of which the Earth's crust is mainly composed. It is made up of minerals, and usually made up of several minerals. Rocks, unlike minerals, do not normally have a definite chemical composition.

4.3. Mineral - A natural inorganic substance which possesses a definite chemical composition (normally a rock does not) and a definite chemical and physical properties. Of the large number of minerals, around two hundred of minerals are abundant, while less than a dozen are common in most rocks.

4.4. Weathering - The decay and disintegration of rocks of the Earth's crust by exposure to the atmosphere, either mechanical or chemical. The work of rain and wind are often not considered weathering as they involve transporting material, and so belongs more strictly to erosion.

4.4.1. Chemical weathering is caused by temperature changes, the dissolving by a solution of rainwater and carbon dioxide, hydration, and oxidation.

4.4.2. Mechanical weathering includes expansion and subsequent contraction of rocks due to changes in temperature between night and day, and frost action when rain water freezes and expands in cracks and pores of rocks.

4.5. Denudation - The wearing away of land by various weathering agents and agents of erosion: the sun, wind, rain, frost, running water, moving ice, and the sea. It is one of the two most major processes responsible for changes to the form of the Earth's surface, the other being deposition.