ROCKS!

Rock – a mixture of minerals, mineraloids, glass, and/or organic matter

James Hutton James Hutton, known as the father of geology, suggested that the Earth was much older and that processes occurring in the present were the same processes that had operated in the past, and would be the processes that operate in the future. This concept became known as uniformitarianism and can be summarized by the phrase "the present is the key to the past"

James Hutton The Father of Modern Day Geology A Philosopher A Scientist An Author

Rock Cycle – a cycle which shows how one rock type changes into another rock type (it’s a never-ending cycle)

The Three Rock Families 1. Sedimentary 2. Igneous 3. Metamorphic

8 processes that show how one rock changes into another: weathering erosion compaction cementation melting cooling heat pressure Sedimentary Rocks Igneous Rocks Metamorphic Rocks

The Rock Cycle

Igneous Rocks

Igneous rocks – formed when magma or lava cools and hardens The classification of Igneous Rocks is based on two things: 1. Cooling location 2. Mineral composition

1. Classification based on cooling location Intrusive Extrusive Porphyry

Intrusive Igneous Rocks – rocks that form by slow cooling beneath Earth’s surface and form large mineral grains (coarse grains) Cool very slowly from magma underground Form large (coarse) mineral grains (this happens because time allows the atoms of the minerals to arrange themselves in a pattern that we can see) Also called plutonic igneous rocks

Intrusive Igneous Rocks Granite Diorite Large/Coarse Grains = Slow Cooling Rate

Extrusive Igneous Rocks – rocks that form by fast cooling on or near the Earth’s surface and form small mineral grains (fine grains) Cool quickly from lava above ground Form small (fine) mineral grains or no mineral crystals at all (no mineral grains form when very rapid cooling occurs) Also called volcanic igneous rocks

Extrusive Igneous Rocks Obsidian Basalt Small/Fine grains or no grains = fast cooling rate

Porphyry – rocks that form by both fast and slow cooling Cool fast and slow, therefore have both large and small mineral grains Large Grains Small Grains

2. Classification based on mineral composition Basaltic Granitic Andesitic

Basaltic – dark colored, high density, rich in iron and magnesium, made from thin, runny mafic lava Examples Basalt Scoria

Granitic – light colored, low density, rich in oxygen and silicon, made from thick, sticky felsic lava Examples White Granite Red Granite

Andesitic – mineral compositions in between basaltic and granitic, made from lava in between basaltic and granitic Examples Diorite Andesite

Formation of Sedimentary rocks: They can form when sediments precipitate (or become a solid) out of solution. 2. They can form when rocks are weathered and eroded into sediments, the sediments are deposited in layers (usually in the ocean), and then the pressure from the upper layers pushes down on the lower layers to compact and cement the sediment to form rock.

Sedimentary rocks form in layers: Youngest Layer 2 Layer 1 Oldest Law of Superposition – in an undisturbed sequence of sedimentary rock, the oldest rocks are found at the bottom and the youngest are at the top

Sedimentary Rock in Layers We call this layering characteristic in sedimentary rock stratification

Classification Sedimentary rocks are classified based on the make-up of the rock

Clastic (detrital) – made from pieces of other rocks that are pressed and cemented together Shale Conglomerate Sandstone

Chemical – made when water evaporates from salt lakes and shallow seas Limestone Rock Salt

Coquina Bituminous Coal Chalk Organic – made when dead plants or shells form thick layers and get pressed and cemented together Coquina Bituminous Coal Chalk

Some Unique Characteristics of Sedimentary Rock Fossils Ripple Marks Geodes Mud Cracks

How was coal formed?

More about coal Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons. It is the most abundant fossil fuel produced in the United States. Coal Vein

Coal is a nonrenewable energy source because it takes millions of years to create. The energy in coal comes from the energy stored by plants that lived hundreds of millions of years ago, when the earth was partly covered with swampy forests. For millions of years, a layer of dead plants at the bottom of the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. The heat and pressure from the top layers helped the plant remains turn into what we today call coal.

Types of Coal Coal is classified into different types depending on the amounts and types of carbon it contains and on the amount of heat energy it can produce. The rank of a deposit of coal depends on the pressure and heat acting on the plant debris as it sank deeper and deeper over millions of years. For the most part, the higher ranks of coal contain more heat-producing energy

4 Main Stages of Coal Peat Lignite Bituminous Coal (Sedimentary) Anthracite Coal (Metamorphic)

Lignite is the lowest rank of coal with the lowest energy content Lignite is the lowest rank of coal with the lowest energy content. Lignites tend to be relatively young coal deposits that were not subjected to extreme heat or pressure. Lignite is crumbly and has high moisture content.

Bituminous coal contains 45-86 percent carbon, and has two to three times the heating value of lignite. Bituminous coal was formed under high heat and pressure. Bituminous coal in the United States is between 100 and 300 million years old. It is the most abundant rank of coal found in the U.S., accounting for about half of U.S. coal production.

Anthracite contains 86-97 percent carbon and its heating value is slightly lower than bituminous coal. Anthracite is very rare in the United States. The only anthracite mines in the United States are located in northeastern Pennsylvania. Anthracite Coal is a Metamorphic Rock that is made after Bituminous Coal undergoes heat and pressure

Metamorphic Rocks ROCKS

Metamorphic rocks – rocks that have changed due to temperature and pressure increases Metamorphic rocks can undergo changes in composition. Metamorphic rocks can be formed from changes in igneous, sedimentary, and even other metamorphic rocks.

Metamorphism can be regional or local Regional – mountain building Local – smaller areas Contact – hot magma melts nearby rocks Deformational – high pressure areas at faults

Local vs. Regional

Classification Metamorphic rocks are classified based on the texture of the minerals in them

Types of Metamorphic Rocks Two types of Metamorphic rocks: Foliated Nonfoliated (Unfoliated)

Examples of Foliated Metamorphic rocks: 1. Foliated – formed when existing rock (parent rock) is placed under great heat and pressure and the mineral crystals flatten out into parallel bands Examples of Foliated Metamorphic rocks: Parent Rock Metamorphic Granite Gneiss Basalt Schist Shale Slate

Foliated Examples Slate Gneiss Schist

Before and After Granite (Igneous Rock) Gneiss (Metamorphic Rock)

Examples of Unfoliated Metamorphic rocks: 2. Unfoliated – form when existing rock (parent rock) is placed under great heat and pressure and the mineral crystals are not arranged in parallel bands Examples of Unfoliated Metamorphic rocks: Parent Rock Metamorphic Sandstone Quartzite Limestone Marble

Unfoliated Examples Quartzite Marble