Processes of Rock and Soil Formation Geology Review Processes of Rock and Soil Formation

Mineral Formation Minerals are naturally-occurring solids. Minerals are formed when magma or lava cools. Minerals are also formed when water evaporates out of chemical solutions.

Minerals Naturally-occurring solids Minerals are substances found in nature. Minerals are solid. Minerals are inorganic. Minerals are made of atoms. Some minerals are made of only one kind of atom. Most are made of different types of atoms There are more than 3,500 different kinds of minerals on Earth.

Mineral Properties Color: Color is not the best identifying property. Hardness: Moh’s hardness scale: 1 to 10 Streak: The colored line a mineral makes on a plate. Cleavage and fracture: How a mineral breaks. Luster: The amount of light reflected. Crystal Shape: Atoms arrange in specific patterns depending on the mineral Fluorescence: Glow in black light Magnetism: An attractive force within some minerals

Mineral Uses Minerals are used for many different types of things.

Rocks Rocks are made of minerals. Sheets of rock lie beneath Earth’s soil and water. This part of the Earth we call the crust. Most of the rocks we see are pieces that have broken off Earth’s crust. They are classified by their formation and composition.

Igneous Rocks Igneous rocks are made deep inside Earth. These rocks are made from magma. Magma is melted rock deep inside Earth. When magma cools, it becomes solid rock. Sometimes magma flows out of holes in Earth’s crust called volcanoes. When lava cools it also hardens into igneous rocks. Some rocks cools slowly and some cool quickly.

Types of Igneous Rocks Granite Obsidian Scoria Basalt Pillow Basalt Pumice

Metamorphic Rock Metamorphic rocks are made out of other kinds of rock. Heating and squeezing change the minerals inside the rock and they become metamorphic. Rocks are pushed and squeezed inside Earth. Sometimes the tectonic plates push against one another forcing the rocks to be squeezed together.

Metamorphic rocks Marble Gneiss Garnet Slate Rose Quartz

Sedimentary Rocks Sedimentary rocks form on Earth’s surface of just beneath it. They are made of small pieces called sediments. Sediments can be mud, sand, stones, shells or bone. When sediments harden together, they become sedimentary rock.

Types of Sedimentary Rock Chert Bauxite Breccia Shale Conglomerate Coquina

Rock Cycle Rocks are part of a cycle, or pattern, that happens again and again. The rock cycle changes old rocks into new ones. Water, wind and ice change rocks. Heat changes rocks. Movement can push rocks inside Earth.

Forces within the Cycle

Weathering & Erosion Weathering is the wearing down of rock over time. Erosion is when rocks are carried by water, wind or ice.

Deposition This is the process where rock and sediments are carried and then deposited in a certain area.

Weathering Weathering is the process that decomposes or breaks down exposed rock. One type is chemical Another type is mechanical

Weathering Formations Bridges and arches form when rocks have been weathered and eroded.

Weathering Chemical Mechanical

Fossils Fossils are the hardened remains of plants and animals that lived more than 10,000 years ago. Fossils are also the traces and evidence of plants and animals that lived more than 10,000 years ago.

Fossil Types Preserved remains Carbon Films Mineral replacement Molds & casts

Preserved Fossils Fossils are plant and animal remains that have been naturally preserved. Most remains disappear over time. Fossils that remain usually get buried and the remains are protected. They are hidden from animals and are safe from water and wind. Index fossils were species that were abundant and then became extinct rather quickly.

Deposition Deposition is when sediments that are carried are deposited. It is because of deposition that many fossils are preserved.

Relative Age This is a way of finding the relative order of past events without determining their absolute age. Fossils are often used to correlate on stratigraphic column with another. Index fossils are most useful in determining relative age.

Law of Superposition The Law of Superposition states that: In undisturbed rock layers, the oldest rocks are on the bottom. Unless some force disturbs the layers after they were deposited, each layer of rock is younger than the layer below it.

Law of Horizontality Most rock-forming materials are deposited in horizontal layers. Even though they might be tilted, all the layers were originally deposited horizontally.

Intrusions and Extrusions One of these is from magma (intrusions) and one of these is from lava (extrusion). Both of them are younger than the layers they cut through.

Earthquake Earthquakes occur when there is movement caused by the breaks in Earth’s lithosphere.

Earthquakes An earthquake is what happens when two blocks of Earth suddenly slip past each other. Tremendous vibrations occur with the energy traveling in waves. Earthquakes have tremendous amounts of kinetic energy. The location directly above it on the surface of the Earth is called the epicenter.

Folding and Faulting plate boundaries Faulting occurs when Folding occurs when rock is compressed as it is along colliding plate boundaries These normally happen as a result of an earthquake Faulting occurs when enormous stresses Build up and push intact rock layers beyond their limit.

Volcanoes The Earth has its own internal heat source that provides energy for our dynamic planet. A volcano is a vent in Earth’s crust through which lava, steam and ashes are expelled.

Volcanoes and Energy Geothermal energy is produced within the Earth’s core and is the force for the volcano. Very high temperatures are continually produced inside the Earth by the slow decay of radioactive particles. Magma comes close to Earth’s surface by the edges of the plates where volcanoes occur. Geothermal energy is a renewable source produced deep within the Earth. Most volcanoes occur at plate boundaries.

Hot-Spot Volcanoes These volcanoes are far from plate boundaries. They are believed to be caused by convection currents in the mantle.