Rocks Geology Modern Geology is said to have

Rocks. • Geology • Modern Geology is said to have begun in 1795. James Hutton • Uniformitari • “The present is the key to the past” anism • The geologic processes now at work were also active in the past. • And the present physical features of Earth were formed by these same processes at work over long periods of time.

Three Groups of Rocks. • Rock 3 classifications of Rocks. • A group of minerals bound together in some way. • Atoms, elements, molecules minerals , rocks. • Igneous , Sedimentary , and Metamorphic. • All Classified by origin and composition. • Where they are formed and what materials make them up.

• Igneous • Sedimentary • Metamorphic • Rocks are formed by the cooling and hardening of hot molten rock from inside Earth. • This hot molten rock is called Magma. • Rocks formed by the hardening and cementing of layers of sediments. Come from other rocks. • Are rocks that undergo a change due to heat and pressure underground.

Sedimentary Rocks Metamorphic rocks Igneous rocks

Igneous Rocks • Formation • Plutonic Rocks • Igneous rock either forms at or near the earth’s surface or deep within the earth’s crust. • Or intrusive Igneous rocks. Form underground from cooling magma. These rocks are seen at the surface only when the over lying rocks have been worn away.

• Plutonic rocks develop larger crystal structure because of their slow cooling rate. • Volcanic Igneous Rocks • Or extrusive rocks that form at or near the surface • Have a very fast cooling rates. Crystal structure is very hard to see.

Volcanic Plutonic Identify these as either volcanic or plutonic.

Magma and Lava Types. • Magma • Lava • Two types: • Molten rock underground. • Molten rock at the earth’s surface. • Liquid rock that is thick and slow flowing very high in the mineral SILICA are called Felsic rocks. • This type forms rocks like Obsidian at the surface or Granite under the surface. Forms light colored rocks. • Silica is the key ingredient.

• Mafic magma/lava is the second type. Hotter, thinner and more fluid than felsic. Produces dark colored rocks. It has a low silica content. Forms rocks like basalt at the surface. • Textures- • Igneous rocks are grouped also by their textures. Or in other words the size shape and arrangement of its mineral crystals. • Crystal size is the most important factor. • This depends on how fast the magma cools.

• Types of textures • Note • Smooth grained texture: has no visible crystals. • Coarse Grained texture: Has visible crystal. • Glassy Texture. Has the appearance of glass. • Porferitic texture. Has two distinct crystal sizes. Due to two cooling rates. • When rock is in the liquid state, its atoms are free to move around arrange into crystals. The longer the magma stays liquid the larger the crystals. • Magma has dissolved gas and the more gas dissolved in the magma the larger the crystals grow.

Smooth Porferitic Coarse Glassy

Common Igneous rocks. • Granite • Coarse grained Igneous rock. Common rock in the rocky mtns. • Several types according to mineral content. • Visible crystals • Composed of light colored minerals, quartz, feldspar and some hornblende.

The addition of various minerals like olivine makes granite different colors.

Basalt • Basalt • Most common igneous rock. • Forms at or near the surface by cooling lava and magma. • Cools very quickly • No visible crystals. Fine grained rock. • Often has vesicles. Holes or voids in the rock where volcanic gasses were trapped by the solidifying material.

Rhyolite • Rhyolite • Composed of the same light colored minerals as in granite. • Cools at or near the surface very quickly. • Is fine-grained.

Obsidian • Obsidian • Dark colored igneous rock however, has a composition similar to Granite. • Cools very quickly at the surface. • Glassy texture. • Had many uses for Native Americans due to its unique way of breaking.

#1 Igneous Topic Questions 1. Before James Hutton , how had geologists explained the origin of landforms like mountain ranges? 2. Name and describe the 3 main groups of rocks. 3. Describe the difference between intrusive and extrusive rocks. Give their other names. 4. Name & describe the FOUR types of rock textures. 5. Draw a detailed piece of granite (colored) & label the minerals that compose it. [pg. 95 red text] 6. In at least 50 words describe how a porphyritic texture happens in an igneous rock.

Sedimentary Rocks • Sedimentary Rocks • Rocks made of other rocks. • Three types. Clastic, Organic and Chemical. • Sedimentary rocks are classified by their origin. • Although most of the Earth’s crust is made of igneous rock, most of its surface is covered by sedimentary rocks.

• Clastic sed. • Clasts are fragments of other Rocks rocks that range in size from boulders to silt and clay particles. • When clasts get stuck together by natural cements like silica or calcite they form clastic sedimentary rocks. • Examples • Shale, sandstone and conglomerate.

Clastic Sedimentary Rocks

• Chemical Sed. Rocks • Sedimentary rocks are formed from mineral grains that fall out of a solution by evaporation or by chemical action. • Rock salt and limestone are examples of chemical sedimentary rocks.

Lake drying in the sun. Water evaporates and leaves the dissolved minerals behind creating chemical sedimentary rocks.

• Organic Sedimentary Rocks • Sedimentary Rocks are formed from the remains of plants and animals. • Coal and limestone made of shell fragments are also examples.

Fossils in Sedimentary Rocks • Fossils • Remains or impressions of plants and animals preserved in a rock. • Sedimentary rocks are the only rock type that you will find fossils. • As sediments pile up, animals and plants that die in the area are buried. The soft parts dissolve away and decay. The hard parts may remain as a fossil.

Uncommon Fossils • Copralite- Petrified dinosaur droppings.

Stramatolite Stromatolite, layered deposit, mainly of limestone, formed by the growth of blue-green algae (primitive one-celled organisms).

Nodules Concretions and Geodes • Nodules- odd shaped lumps formed in limestone hollows and voids made of fine grained silica. • Concretions- Round masses of calcium carbonate that often occur in layers of shale. Formed from a solution around a central ionized particle. • Geodes- Limestone sometimes contains round hollow pockets that fill up with crystals. Formed by groundwater that has dissolved some quartz or calcite crystals.

• Sedimentary Review 1. What Rock type is the only one that will contain fossils? 2. Name three types/classes of sedimentary rocks. 3. In the blue text look up and define the following. Stratification, Geodes, Concretions, and Nodules. 4. What kinds of materials can act as mineral cement in clastic sedimentary rocks? 5. Name the rocks that are formed from each kind of sediment. Sand, Mud, Clay, Sharp pebbles, rounded rocks, dissolved animal shells,

Copy Summery Table of Common Sedimentary Rocks in your notes. • Pg. 74 blk text.

Metamorphic Rock • Formation • All of the metamorphic rock are rocks that undergo some type of change due to intense heat and pressure. • The type of pressure needed to change a rock’s structure can only be achieved at great depths in the earth’s crust. • Two types. • Regional and Contact Metamorphism. • Occurs when large areas of rock are under intense heat and pressure. • Pressure squeezes their grains closer together. The squeezing makes them more dense and less porous.

• The heat and chemicals may rearrange the particles. Making lines and bands in the rocks. Contact Metamorphism. Diagram • This process occurs when hot magma forces its way into overlying rock. The heat of the magma bakes the rocks that are in contact with it. Relation of common Sedimentary materials and rocks and the metamorphic rocks pg. 78 blk text.

Examples of metamorphic rocks and their origin rock.

Formation of Gneiss • Forms when Granite or Conglomerate rock is changed.

Rock Cycle & Rock Review Comp book Assignment Define Metamorphic Rock and list 4 examples. Compare and contrast the difference between regional and contact metamorphism. List the general changes seen in rocks caused by metamorphism. Red Text…. 1. Reviewing Key Terms pg. 119 #’s 1 -6 2. Checking Concepts pg. 120 #’s 7 -12 3. Applying Skills pg. 120 #’s 17 -20