April 27th Review

Drill: You find an igneous rock with both coarse and fine grains. Describe how this rock could have formed.Objective: SWBAT review basic concepts of the Rock Cycle in order to prepare for the test.

Rocks

Igneous: Formed by molten material either lava or magma.Sedimentary: Created from compaction and cementation of layers of sediment and remains of organisms.Metamorphic: When a rock undergoes extreme heat and pressure causing it to change forms.

Sedimentary Rocks

Formed over millions of years.Compaction: Pressure from layers (and/or oceans) above.Cementation: Minerals dissolved to form materials that bind the sediment together.****Fossils normally found in this type of rock.****Typically rock forms in layers

Types of Sedimentary Rocks

Clastic: Larger pieces of sediment that form rocks under pressure.Organic: Rocks formed from living materialsChemical: Rocks that are “glued” together through mineral solution.

Comparing RocksTexture:

Grain SizeCoarse vs. Fine

Grain ShapeSmooth & roundedRough & jagged

Grain PatternFlat layersWavy, swirlingRows of beadsNo pattern

No Visible Grain

Mineral Composition:

MicroscopeAcid testMagnetic

Origin:IgneousSedimentaryMetamorphic

Igneous

Formed from volcanic materialIntrusive: Formed from magma in the EarthExtrusive: Formed from lava on top of the layers.Grain size is determined by cooling rate.

Metamorphic Rocks

Form from existing rock exposed to extreme heat and pressure.Folliated: Rock arranged in layers or bands.Non-folliated: Random patternContact Metamorphism: Rock comes in contact with an intrusion of magmaFault metamorphism: Rock exposed to extreme pressure from plate movement.

Rock Cycle

Rocks can change from one type to another through a series of events.Weathering and Erosions – Sediment – Compaction/Cementation = Sedimentary rocks.Melting – magma – cooling = Igneous rockExtreme Heat and Pressure = Metamorphic