Rock Cycle

Goals You will be able to identify the basic characteristics of different types of rocks You will be able to label and identify all of the steps in the rock cycle and locate where specific types of rock are formed.

A picture of the Cycle…

3 Main Classifications - Igneous- Rocks formed from previously melted rocks -Sedimentary- Rocks formed from fragments of other rocks and minerals that have undergone lithification -Metamorphic- Rock that has changed from one type to another

Igneous Most often associated with Volcanoes.

Classified by texture and mineral composition

Igneous Molten rock from some source cools into solid rocks. 2 main classifications◦Intrusive◦Extrusive

Igneous Intrusive Igneous rocks that “intrude” into the space other rocks are already occupying

Igneous Intrusive The depth and temperature of where the rock form determine the physical properties of the rock.

Igneous Intrusive (Course Grain) Large xl’s (crystals) indicate the rock formed at high temperatures over a very long time.

Course Grained Granite

Igneous Intrusive (Fine Grain)

Small xl’s indicate the rock formed very quickly. The smaller the xl, the faster the formation

Fine Grained Granite

Igneous Extrusive Rocks that are produced when magma from below the surface becomes lava and cools.

Lava from volcanic eruption

Igneous Extrusive Depending on the type or eruption, different materials are formed.

Fast cooling, large volume of dissolved gasses- Pumice

Extremely fast cooling, no dissolved gasses, results in glassy texture- Obsidian

Sedimentary

Sedimentary Sedimentary rocks are formed from particulates from other rocks.

These particulates are cemented or compacted together.

Sedimentary 75% of all rock outcrops on continents are sedimentary.

Only 5% of the Earth’s crust is Sedimentary.

Sedimentary- Lithification Cementation and compaction are the methods that form Sedimentary Rocks.

Sedimentary Limestone is highly porous and will hold water.

Sedimentary 2 classes of sedimentary rocks

◦Detrital ◦Chemical

SedimentaryDetrital These are chunks of other rocks that have broken off for some reason.

Gravel Breccia

Sedimentary Detrital Sandstone and shale are made from sand and clay respectively.

Sedimentary The chunks come from weathering and erosion. ◦Weathering- above ground◦Erosion- associated with water

Sedimentary Detrital The type of detrital sedimentary rock is determined by the size of the particle.

Sedimentary Chemical Rocks that form when dissolved materials precipitate out of solution and form rocks. Dover, England- LimestoneCoquina- Seashells that have fragmented and cemented together

Sedimentary Chemical Evaporites- Rocks that form when water evaporates and leaves dissolved minerals behind.

Salt flats that result from water picking up salt and other minerals like calcium carbonate in the mountains and running down to a lakebed where the water evaporates.

Metamorphic Literally- rocks that have changed

Gneiss- More aligned than most other types of rock, variable mineral composition

Michaelangelo’s David- Marble- Started as limestone that was heated

Metamorphism Types ◦Regional◦Contact

Metamorphism Regional Most common type

◦Large scale deformations◦Usually caused by pressure from the tectonic plates squeezing rocks

Metamorphism Regional Most mountain ranges will result in regional metamorphism.

Metamorphism Contact Happens in places where magma or lava partially melt rocks and change them.

Grades of Metamorphism Low grade- Rocks are subjected to temperatures and pressures only slightly greater than their original environment.

Slate- started as shale

Grades of Metamorphism High grade- results from situations where temperatures are much higher than when the rock formed.

Foliation- flat characteristic of the rockVisible seams and color variations in those indicate high pressure squeezing of soft (melted) material.

Metamorphic Agents of metamorphism◦Heat◦Pressure◦Chemical Change

Metamorphic Heat Usually associated with contact metamorphism.

Metamorphic Pressure Caused almost purely by squeezing the rocks together.

Metamorphic Chemical A solvent, typically water, dissolves and/or deposits minerals.

Characteristics of Metamophosed Rocks Tend to be more organized.

Granite

GneissNon-foliated granite might become foliated Gneiss.