1. Igneous Rocks:
* Origin: Magma is molten rock found beneath the Earth's surface. It contains a variety of minerals dissolved within it.
* Formation: When magma cools and solidifies, it forms igneous rocks. The specific minerals that crystallize depend on the composition of the magma and the cooling rate.
* Examples: Granite, basalt, obsidian.
2. Sedimentary Rocks:
* Origin: Igneous rocks, and even existing sedimentary rocks, can be weathered and eroded by wind, water, and ice. This breaks down the rocks into smaller fragments called sediments.
* Transportation: Sediments are transported by rivers, streams, wind, and glaciers. Minerals within the original igneous rocks are carried along in this process.
* Deposition and Lithification: Sediments settle and accumulate in layers. Over time, these layers are compressed and cemented together by minerals dissolved in groundwater, forming sedimentary rocks.
* Examples: Sandstone, limestone, shale.
3. Metamorphic Rocks:
* Origin: Igneous or sedimentary rocks can be transformed into metamorphic rocks by intense heat and pressure deep within the Earth's crust.
* Transformation: The heat and pressure cause the minerals within the original rocks to rearrange and recrystallize, forming new mineral assemblages.
* Examples: Marble (from limestone), slate (from shale), gneiss (from granite).
The Rock Cycle in a Nutshell:
The rock cycle is a continuous process where rocks are constantly being transformed from one type to another. Minerals from magma, the source of igneous rocks, are recycled through the cycle as follows:
1. Igneous to Sedimentary: Weathering, erosion, transportation, deposition, and lithification transform igneous rocks into sedimentary rocks.
2. Sedimentary to Metamorphic: Heat and pressure transform sedimentary rocks into metamorphic rocks.
3. Metamorphic to Igneous: Metamorphic rocks can be melted back into magma, restarting the cycle.
4. Igneous to Metamorphic: Igneous rocks can be transformed into metamorphic rocks through heat and pressure.
Key Points:
* Mineral Recycling: The rock cycle is a process of constant mineral recycling. Minerals are never truly "destroyed," but are continually re-formed into new rock types.
* Composition: The specific minerals in a rock depend on the original magma composition and the conditions of transformation during the rock cycle.
* Continuous Process: The rock cycle is a dynamic process, constantly happening on Earth's surface and within its crust.
