The Rock Cycle Rock Cycle The Rock Cycle

The Rock Cycle

Rock Cycle • The Rock Cycle is: – A process in which a rock is able to change into other types of rocks. – Types include: • Igneous • Sedimentary • Metamorphic

Where are rocks found? • • • EVERYWHERE!!!! On top of Mountains Under Mountains Volcanoes Rivers Lakes

Igneous Rocks • Igneous means: From Fire • Form from the cooling of magma or lava. • Magma is inside the Earth • Lava is outside the Earth

How are Igneous Rocks Classified? • They are classified by their texture and composition. • Texture can be coarse-grained or finegrained. – Coarse-grained • Feels Rough • Has Crystals – Fine-grained • Feels Smoother • Has little or no crystals

Coarse-Grained • Has crystals because the rock cooled SLOWLY • Coarse-grained rocks are also known as INTRUSIVE because they cooled inside the Earth from MAGMA.

Fine-Grained • Has no crystals because the rock cooled QUICKLY (or fast). • Known as EXTRUSIVE because they form on the surface of the Earth from LAVA.

Composition • Two types of composition: Felsic Minerals – Mafic • Made out of dark minerals – Felsic • Made out of light minerals Mafic Minerals

What type of Igneous Rock is this? ? ? Intrusive or Extrusive? Felsic or Mafic?

Sedimentary Rocks Sediment – Broken pieces of rock Sedimentary Rock – A rock made out of sediment

Sedimentary Rocks • Steps of Sedimentary Rock Formation – Weathering – Erosion – Deposition – Compaction – Cementation Sedimentation

Sedimentary Rocks • Weathering – The mechanical or chemical processes that cause exposed rock to break into sediment. • Mechanical Weathering – Rock is broken down by physical types of weather • Chemical Weathering – Rock goes through chemical changes, that break down the rock

Mechanical Weathering • Temperature – High Temperature causes water in rocks or soil to evaporate, creating cracks in the ground. – Low Temperature causes rocks to contract during the winter, then during the spring and summer the rock expands, causing it to crack.

Mechanical Weathering • Frost Weathering – Temperature drops below freezing – Water inside of a rock freezes – Water expands when it freezes – Expansion pushes sides of rock apart – During Spring, ice melts.

Mechanical Weathering • Abrasion – Water crashes against the rock • Over time the rock becomes sand on a beach – Wind hits the rock repeatedly • Over time the rock becomes sand in a dune

Mechanical Weathering • Biological – Plants or animals break rock down – Plant • Roots from a tree force rock to break and the root goes into the cracks. • Lichen or Moss attach to the rock and break it down into dirt.

Chemical Weathering • Breaks down rock and changes the composition of the rock – Acidification • Rock dissolves from exposure to acid in water – Oxidation • Iron in rocks combine with Oxygen and cause rock to form rust (red)

Erosion • Erosion – moves sediment by wind or water and gravity • Water – Rain – Rivers – Glaciers – Waves – Flooding

Erosion • Wind – carries small pieces of sediment and drops them somewhere else • Gravity – pulls down sediment towards the Earth. – Rock Slides

Weathering and Erosion

Deposition • The build up of sediment • Sediment being carried in wind or water, eventually drops out of the wind or water and settles onto the ground. • Happens at the bottom of lakes or in sand dunes, etc.

Compaction and Cementation • Compaction squeezes sediment together – As sediment is squeezed, some of the minerals become liquid, creating mineral glue • Cementation glues sediment together

How are Sedimentary Rocks Classified? • Texture: Sediment comes in all shapes and sizes. Size and shape can help determine the environment in which the rock formed. – Clay and Silt < 1/16 mm (Cannot see with unaided eye) – Sand 1/16 mm to 2 mm – Gravel > 2 mm • Composition: The minerals the rock is made out of. Limestone is made out of Calcite, which reacts with acid. Other rocks can also have fossils, which also react with acid.

Texture

Composition

Metamorphic Rock • Metamorphic – Means Change Shape • Formed by heat and pressure, NO MELTING!!! • Types of Metamorphism – Contact – Regional

Contact Metamorphism • Over millions of years rocks are pushed further and further underground • Magma intrusions cut through rock layers • Rocks near the intrusions are exposed to heat and pressure • Minerals rearrange/recombine to form new minerals • Mineral grains are flattened by pressure

Contact Metamorphism

Regional Metamorphism • Metamorphism occurs over a large area • Rocks changed by heat and pressure • Rocks closer to plate boundaries have the most heat and pressure

Foliated vs. Non-foliated • Foliated – sheet-like layering caused by shearing or differential pressure (higher pressure from one direction) • Non-foliated – no layering, rocks under heat and pressure, but there is no shearing or not enough pressure in one direction