Rocks

What are Rocks? Rocks are a combination of minerals that are bonded together in some way. All rocks are made of minerals Monomineralic- contain one mineral Polymineralic- contain more than one mineral Rocks are classified into three groups by how they are formed

3 types of Rocks Metamorphic Rocks: are formed when old rocks change by heat and pressure. Sedimentary Rocks: Form from sediments (pieces of other rocks) that are cemented together. Igneous Rocks: Form from molten rock that cools and hardens. Rocks are classified by how they form

Classification of igneous rocks- 2 types Intrusive Form from magma Cooled and solidified (hardened) slowly deep underground Large crystal size Extrusive Form from lava Cooled and hardened quickly at or near the surface of the earth. Small or no crystals

Igneous rocks are also formed causing the magma to rise when volcanoes erupt, causing the magma to rise above the earth's surface.

Types of igneous rocks Granite- most abundant igneous rock Can be made up of feldspar, quartz, mica, and hornblende

Obsidian Obsidian rocks are igneous rocks that form when lava cools quickly above ground. Obsidian is actually glass and not a mixture of minerals. The edges of this rock are very sharp.

Pumice Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground. This rock is so light, that many pumice rocks will actually float in water. Pumice is actually a kind of glass and not a mixture of minerals.

Extrusive Insrusive

Igneous Rocks Can be: Felsic: light colored rocks that are rich in elements such as aluminum, silicon. Lower density Mafic: dark colored rocks that are rich in iron and Mg. Higher density Coarse-grained texture: takes longer to cool, larger visible mineral crystals Fine-grained texture: cools quickly with small mineral crystals Glassy Texture: cools the quickest, no mineral crystals form Vesicular texture: Gas pockets (holes) (note) Texture refers to the size/appearance of the minerals

II. Sedimentary Rocks

How are they formed? Fragments of rock get broken down into sediments ARE USUALLY FORMED IN A WATERY ENVIRONMENT. OFTEN LAYERED ARE THE ONLY ROCKS THAT CONTAIN FOSSILS Fragments of rock get broken down into sediments Sediments are transported, compacted, and cemented into rock

Sedimentary Rocks: Are the only type of rocks that contain fossils. Fossil formation http://www.classzone.com/books/earth_science/terc/content/visualizations/es2901/es2901page01.cfm

Clastic Rocks – fragments cemented together and include the sediments: sand, silt, clay, pebbles, and boulders

Chemical rocks (crystalline) result of evaporation Generally these rocks are formed from one mineral Rock salt (halite) Rock gypsum- made from gypsum

Organic rocks (contain remains of living things) Or Bioclastic Limestone- made from Mineral calcite and Fragments of shells Bituminous coal- fossil fuel Formed from plant remains in Swampy areas- most are millions Of years old

3. Metamorphic rocks

Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change.

These pre-existing rocks are called parent rocks How are they formed? Metamorphic rocks are pre-existing rocks that have been changed by heat and/or pressure without melting. These pre-existing rocks are called parent rocks

Classification- 2 groups Foliated Mineral crystals are aligned, or arranged in bands or layers. Banding: High grade metamorphism. Alternating layers of dark and light minerals. Non-foliated Mineral crystals do not have mineral crystals arranged in bands of layers. Example marble and quartzite.

Metamorphism Regional Metamorphism Contact Metamorphism Caused by extreme pressure and heat. Happens over wide “regions”. Contact Metamorphism Caused by contact with extreme heat.

Holey schist!

Rock Cycle Rock must go through melting and solidification to become an igneous rock Rock must go through weathering and erosion to become sedimentary rock Rock must go through heat and pressure to become a metamorphic rock

Based on the characteristics, what kind of rock is A. B. C. D. E Based on the characteristics, what kind of rock is A? B? C? D? E? Write the key word that led you to this conclusion.