ALL ABOUT ROCKS Learning Objectives 1 Learn everything

ALL ABOUT ROCKS Learning Objectives: 1. Learn everything you need to know about sedimentary rocks. 2. Learn everything you need to know about igneous rocks. 3. Learn everything you need to know about metamorphic rocks. 4. The Rock Cycle

Sedimentary Rock Formation • Sedimentary rocks are made from sediment, small pieces of rock (any type). • How is sediment formed? • Weathering

Sedimentary Rock Formation (Steps) 1. Weathering 2. Erosion 3. Transportation 4. Deposition 5. Compaction 6. Cementation

Weathering • Weathering = wearing away • Types of weathering • Chemical • Physical

• Chemical weathering = weathering caused by substances in air or water having a chemical reaction with the rock

• What type of chemical do you think weathers rocks? • ACID • Rainwater is slightly acidic because carbon dioxide reacts with water to for carbonic acid. • However, acid rain from pollution is a stronger acid and weathers rocks more quickly.

Practical: Chemical weathering • Put a few drops of dilute acid onto the different types of rocks and write down your observations.

• Physical weathering = weathering caused by physical changes such as: • changes in temperature • freezing and thawing • the effects of wind, rain, and water.

Physical Weathering Examples Freeze-Thaw Weathering Onion Skin Weathering

Physical Weathering Examples Glacial Weathering

Weathering happens to all rocks • Suggest which type you think will weather the fastest and explain why. • Sedimentary • Weakest bonds between the grains • Porous, water/acid will get into the rock and weather from the inside or freeze and break the rock.

Erosion = pieces of rock fall off

Transportation = sediment is moved to lakes or seas • Movement of wind, water, or ice (glaciers) moves the sediments towards the ocean.

Deposition = sediment falls to the bottom of the sea and builds up in layers

Compaction = the layers on the bottom are compressed from the weight of the layers on top • The pressure from the weight of the sediments on top squeeze the water out from between the grains.

Cementation = dissolved minerals “glue” the sediments together • When the water is squeezed out, dissolved minerals are left behind act as a glue cementing the sediments together.

Formation of Igneous Rocks • Magma = molten (hot liquid) rock deep underground • Lava = magma that is above ground • Igneous rocks are formed when magma or lava cools and solidifies.

Crystal Size Depends on the Speed of Cooling • Extrusive igneous rocks – magma “exits”, lava cools quickly in the air and forms rocks with small crystals (not enough time for crystals to grow) • Intrusive igneous rocks – magma is “in” the ground, magma cools slowly underground and forms rocks with large crystals

Crystal Size Depends on the Speed of Cooling Fast Cooling Above Ground Slow Cooling Below Ground

Metamorphic Rock Formation • Metamorphic rocks are formed when rocks are under high heat and high pressure from being deep underground.

The high heat and high pressure makes the rocks have a chemical change. The high pressure is what causes the crystals to be flattened.

Rock Cycle High Heat and Pressure Weathering, Erosion, etc. Melting and Cooling