Rocks and rock cycle By: Rashid And Andrew

Introduction  Rock is the most and abundant material on earth.  When rocks are examined it consists of smaller crystals or minerals.  Minerals- are chemical compounds with its own composition and physical properties  Texture- the size, shape, and arrangement of its minerals.

Basic Rock Types  Igneous Rocks  Sedimentary Rocks  Metamorphic Rocks

Igneous Rocks  This rock forms when molten rock called magma cools and solidifies. Magma is melted rock that can form at various levels deep within the earths crust and upper mantle.  Igneous rocks are divided into two types :  Intrusive rocks - Coarse grained igneous rocks that form far below the surface are called intrusive rocks.  Extrusive rocks – igneous rocks that form at earths surface are described as extrusive rocks.

Sedimentary Rocks  Sedimentary Rocks- accumulate in layers at earth’s surface. They are materials derived from preexisting rocks by the process of weathering.  Weathering- Physically break rock into smaller pieces with no change in composition. Other weathering processes decompose rocks and that chemically change minerals into new minerals and into substances that readily dissolve in water.  Beds- Are products of weathering which are usually transported by water, wind, or glacial ice to sites of deposition where they become flat layers.  Sediments are commonly turned into rock or lithified.  Compaction- takes place as the weight of overlying materials squeezes sediments into denser masses.

……….  Cementation- occurs as water containing dissolved substances percolates through open spaces between sediment grains.  Detrital Sediments- Sediments that originate and are transported as solid particles.  Detrital sedimentary Rocks- Rocks that are formed by Detrital sediments.

Metamorphic rocks  These rocks are produced from preexisting igneous, sedimentary, or even other metamorphic rocks. Every metamorphic rock has a parent rock – the rock from which it formed. Metamorphic means to change form.  During metamorphism, the rock must remain essentially solid.

Three settings of metamorphic rocks :  Thermal – change is driven by a rise in temperature within the host rock surrounding an igneous intrusion.  Hydrothermal – it involves chemical alterations that occur as hot, ion rich water circulating through fractures in rocks.  Regional – during mountain building, great quantity of deeply buried rocks are subjected to the directed pressures and high temperatures associated with large scale deformation