EXPLORING ROCKS

What is a Rock? A mixture of minerals, rock fragments, volcanic glass, organic matter or other natural materials Mt. Rushmore in South Dakota is made up of Granite, which contains several minerals

What is the Rock Cycle? http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page02.cfm http://www.youtube.com/watch?v=Aqy-p41VpKU&feature=related #3. What is the Rock Cycle?

Rock Cycle Summary The three major types of rock are igneous, sedimentary, and metamorphic Rock cycle processes do not create or destroy matter (Conservation of Matter) The rock cycle occurs very slowly over time The rock cycle was first discovered by James Hutton in 1788 at Siccar Point, Scotland

How is Igneous Rock formed? When molten rock material, called magma, cools and hardens, igneous rock forms When magma reaches the Earth’s surface and flows from a volcano, it is called lava http://www.discover.tased.edu.au/openit/science_simulations/igneous.swf http://www.youtube.com/watch?v=Ca1tTwun96k

2 Ways Igneous Rocks Form Intrusive – igneous rocks formed beneath the Earth’s surface Harden slowly Extrusive – igneous rocks formed above the Earth’s surface Harden quickly as lava cools

How are Igneous Rocks Classified? Basaltic – dark colored, dense, from magma rich in magnesium and iron. Granitic – light colored, lower in density, formed from magma with lots of silica

Volcanic Glass Occurs when rocks are cooled so quickly that few or no mineral grains form. Pumice and scoria form so quickly that gases are trapped and they leave holes when they eventually escape.

Making Sense of the Rock Cycle Igneous Rocks are the most common rocks on earth, but most are located below the Earth’s surface 75% of the rocks found on Earth’s surface are SEDIMENTARY

What is Sediment? Sediment is loose material such as rock fragments, mineral grains and plant and animal remains Sediment comes from already existing rocks that have been eroded. Sediment is moved by wind, water, ice or gravity. http://www.youtube.com/watch?v=ktf73HNZZGY&feature=related The Grand Canyon

Stacked Rocks Sedimentary rocks form as layer, with the oldest layer on the bottom. Sometimes forces overturn the layers and the oldest could end up on top. X

How are Sedimentary Rocks Classified? DETRITAL from erosion and weathering ORGANIC From the remains of living things CHEMICAL When dissolved minerals come out of solutions

How do sedimentary rocks form? COMPACTION – Pressure from upper layers pushes down on lower layers. If the sediments are small enough they will now stick together. CEMENTATION –If the sediments are large, like sand or pebbles, pressure alone can not make them stick, minerals deposit in the gaps and act like cement. Dissolution of minerals in a solution – the process by which minerals in the solution are left behind. Example: rock salt

DETRITAL from weathering and erosion When rock is exposed to air, water and ice it breaks down, this is weathering (sediment is formed) When the weathered material moves it is called erosion (allows for a build up of sediment)

Organic made up of living things COAL Occurs when dead plants are buried under sediments in swamps. These are compacted over millions of years to form an important source of energy CHALK Made up of microscopic shells. These were formed between 145 and 65 million years ago

CHEMICAL When dissolved minerals come out of solutions When water that is rich in dissolved salt evaporates, it deposits the mineral halite, which forms ROCK SALT. **50 % of rock salt is used for road deicing in winter **10% is used for food

What 2 forces are needed to create a METAMORPHIC ROCK? PRESSURE – rocks beneath the Earth’s Surface are under great pressure from the layers above them HEAT – temperature increases with depth in under the Earth’s crust

Who’s the PARENT ROCK here? depending on the amount of heat and pressure one type of rock can change into several metamorphic rocks Heat pressure Heat pressure shale slate Heat pressure phyllite Heat pressure schist gneiss

What is a Foliated Rock? Examples When mineral grains line up in parallel layers. Examples SLATE It’s foliation makes it watertight, used for paving aroun pools GNEISS It’s foliation shows up in alternating light and dark bands

What is Nonfoliated Rock? In some metamorphic rock, layering does not occur, the mineral grains grow, but no pattern is formed. marble Limestone The Sedimentary parent rock