By: Brianna Lawless
WHAT ABOUT ROCKS?
All rocks are composed of minerals and are classified by how hey are formed. There are three types of rocks which are Igneous, Sedimentary, and Metamorphic.
- Igneous rocks are formed by the melting and solidification of molten rock material.
- They are formed near volcano's
- The main types are formed intrusively which is deep underground where they cool slowly and form larger crystals.They are also formed extrusively which is on earth's surface which cool rapidly and form smaller crystals.
- Sedimentary rocks are formed by the accumulation of sediments.
- They are formed at or near the earth's surface and also found near water
- There are three main types of sedimentary rocks called clastic, crystalline, bioclastic. Clastic rocks are made of different sized particles cemented together. Crystalline rocks are deposited when chemicals perticipate and fall to the oceans bottom. Bioclastic rocks are formed by animal and plant remains.
- Metamorphic rocks are formed when other rocks are exposed to heat & pressure without melting.
- They are formed deep within the ground
- The main types of metamorphic rocks are foliation & banding. Foliation is formed by the alignment of minerals in a rock. Banding is the type of foliation that has wavy colored stripes.
EXAMPLES OF EACH ROCK TYPE
- Basalt rocks are igneous rocks formed extrusively which means it cooled rapidly.
- These rocks have a fine-grained texture and have smaller crystals since they cooled rapidly
- Basalt rocks are found black with higher density and mafic composition
- Siltstone is an inorganic, sedimentary rock.
- It has a clastic texture and the grain size is 0.0004 to 0.006 cm.
- It's composition is made up of mostly quartz, feldspar, and clay materials. It also may contain fragments of other rocks and minerals.
- Is very fine grained
Model showing how rocks and sediment change over time