The Earth’s surface is covered in sedimentary rock This rock is made from sediments. That are cemented together. Sediments are pieces of solid materials that have been deposited from: 1.Wind 2.Water 3.Ice 4.Gravity 5.Chemical precipitation

Sediments comes from: 1. weathering – Whenever the Earth’s crust is exposed at the surface it is being worn away by weathering. A physical and chemical process that breaks rock into smaller pieces.  Chemical weathering is when the rock is dissolved and changed chemically. Ex. Granite page 122 fig.6-1  Physical weathering breaks along physical boundaries (fracture) but do not chemically change. Regardless of the type of weathering the fragments produced are called clastic sediments.

Clastic Sediments Clastic sediments can be huge boulders or microscopic particles. Clastic sediments usually have worn surfaces and round edges. At this time copy chart from page 122 table 6-1 into your note book.

Erosion Erosion is the removal and movement of surface materials from one location to another. Four main agents of Erosion: 1.Wind 2.Moving water 3.Gravity 4.glaciers

Examples of Erosion Ex. Streams become muddy after a rain storm because silt and clay have been added to it. Ex. Dust collecting in your home is another example of erosion. Where do you think the dust comes from? How is it carried into your home?

Deposition Wind can carry particles to higher elevation. But eventually gravity brings it back down. Water carries particles down hill. Deposition is when sediments are laid down on the ground or sink to the bottom of bodies of water.

Lithification As sediments are deposited, layers of sediment are formed. These layers can be more than 8 km thick. These layers are subject to increased temperature and pressure.

Steps in Litification 1. Compaction- The weight of the layers forces the clastic sediment particles to move really close together. Groundwater, oil, and natural gas can be found in the spaces in between the layers.

2. Cementation The temperature in the Earth’s crust increases with depth at a rate of about 30 0 C per kilometer. When sediments are buried 3 to 4 km deep the temperature is high enough to start chemical and mineral changes that cause cementation.

Two types of Cementation 1. When a new mineral, for example, calcite (CaCO 3 ) or iron (FeO 3 ) grows between sediment grains as dissolved material precipitate out of ground water. 2. When the same mineral grains grow larger as more of the same minerals precipitate out from groundwater and crystallizes around them. See fig.6-5 p.125.

Features of Sedimentary Rock Bedding- Horizontal layering. Range from 1mm-several meters thick. Graded bedding- Heavier layers form on bottom. Cross bedding- Inclined layers of sediment move forward across a horizontal surface.

Fossils Best known features of sedimentary rock is fossils. Fossil- when an organism is buried before it decomposes. During lithification parts of the organism can be replaced by minerals and rocks.

Medium Grained Clastics Sand sized rock and mineral fragments. Ex. Sandstone Sandstone exhibits porosity- percentage of open spaces between rock grains. Geologists study the ripples in sandstone to map old stream activity and current flow.

Fine Grain Clastics Consists of fine grained clastics like silt and mud. Ex. Siltstone (silt) Shale (silt and clay) Shale has low porosity and breaks along thin layers.

Chemical Sedimentary Rocks Forms from evaporation when a salt water lake or fresh water lake evaporates. Ex. Great Salt Lake in Utah The sedimentary rocks that form are called evaporates. Ex. Limestone (calcite) Rock Salt (Halite) Rock Gypsum (gypsum)

Organic Sedimentary Rock Formed from the remains of once living things. Ex. Limestone(Some organisms use calcium carbonate to make their shells) Ex. Coal (forms form the remains of plant material). Composed of carbon.

Sedimentary Rock as a Resource Oil Coal Natural gas Uranium (found in sandstone) Phosphate (used as fertilizer) Iron (used to make steel) Limestone (used to make cement)

Metamorphic Lab You have 15 minutes to memorize the names of the metamorphic rocks. Then I will collect the chart. I will ask each of you to identify one rock. You get it wrong it’s a zero. You get it right its 100. This is a quiz grade. There is no lab report for this lab

Causes of Metamorphism When temperature and pressure are high enough to cause changes in: Texture Mineral composition Chemical composition

Coarse Grain Clastics Consisting of gravel size rock and mineral fragments. EX. Conglomerate Breccia

Grades of Metamorphism Different combinations of temperature and pressure result in different types of metamorphism. See fig p Three types are: 1.Low Grade 2. Medium Grade 3.High Grade

Examples of Metamorphism 1. the sedimentary rock shale becomes the metamorphic rock slate. Shale  Slate 2. Sedimentary rocks limestone and dolostone becomes the metamorphic rock marble. Limestone + Dolostone  Marble

Three Ways Metamorphism Can Occur 1. Regional Metamorphism - When temperature and pressure affect large areas. See fig page Contact metamorphism – When molten rock meets solid rock. Ex. Sedimentary rock meets magma or lava.

3. Hydrothermal Metamorphism When very hot water reacts with rock and alters its mineral and chemical composition. Hydro = water Thermal = heat Example, Yellowstone National Park

Questions 1. How can the chemical composition of a rock be changed during metamorphism? 2. What are the three grades of metamorphism? 3. What are the three ways metamorphism can occur? 4. Look at figure 6-14A on page 134. Which mineral undergoes the highest

4. Look at figure 6-14A on page 134. Which mineral undergoes the highest temperature and pressure in the formation of shale? Which undergoes the least temperature and presure?

Textures 1. Foliated- High pressure causes crystals to form flat or needle like structures. 2. Nonfoliated – Do not form flat crystal instead they form blocky structures. 3. Porphroblasts – Some minerals can grow larger than other during metamorphism.

The Rock Cycle Any rock can b changed into any other rock. Ex Metamorphic rocks can be exposed on the Earth’s surface where it can be weathered and form sedimentary rock. Ex. Sedimentary rock can increase in temperature and pressure and from metamorphic rock.

Metamorphic rock can reach its melting point and become magma and as it cools and crystallizes; Can form igneous rock. Copy figure 6-21 on page 139 into your note book.

Questions 1. How can igneous rock become sedimentary rock? 2.How can sedimentary become metamorphic rock? 3.How can igneous become metamorphic rock?