HOW ARE THE THREE TYPES OF ROCK RELATED TO THE THEORY OF PLATE TECTONICS? The Rock Cycle

Plate Tectonic Theory – The Earth’s outer shell (lithosphere) is composed of rigid plates that are moving relative to one another.

Review of Plate Tectonics REVIEW OF PLATE TECTONICS

What moves the Plates? Slab PullMantle Push

Types of Plate Boundaries

Divergent Plate Boundaries Mid-ocean Ridges Where Oceanic Crust is Made!

Youthful Oceanic Crust

Basalt – Rock Type of the Oceanic Crust Remember: Melting the mantle makes mafic magma!! Always

Continental Rifting The creation of new ocean basins

Horst and Graben Formation

Convergent Boundaries Ancient Continental Crust

Convergent Boundaries- Where the Action Is!! Ocean- Continent Continent - Continent Ocean - Ocean Earthquakes Volcanoes

Mt. St. Helens May 18, 1980 Consequences of Convergence Explosive Volcanism

Consequences of Convergence Mountain Building & Rock Deformation

Consequences of Convergence Earthquakes Banda Ache, Dec. 26, 2004

OROGENESIS The Culmination of Convergence

San Francisco Earthquake April 18, 1906 Mag 7.8 Transform Boundaries

Mantle Hotspots Creation of over- thickened oceanic crust

Famous Hotspots Hawaii Yellowstone? Iceland

What does this have to do with rocks?

CREATED BY VOLCANIC ACTIVITY- THINK OF LAVA (SURFACE) AND MAGMA (INTERIOR) AS ITS PARENTS Igneous Rocks

IGNEOUS ROCK - A aggregate (pile) of minerals crystallized (solidified) from molten rock (magma). Major distinctions in rock type are based on: WHERE THEY FORMED- If they cooled slowly inside the earth- intrusive – large visible crystals Or, if they cooled quickly on earth’s surface- extrusive- crystals made be small or not all all there WHAT THEY ARE MADE OF- Light-colored/low density- felsic Dark/heavy- mafic NOW, find examples of each of the above types in your specimens.

Igneous Rocks

Fine-grained = Volcanic Coarse-grained = Plutonic Igneous Environments

Creation of Igneous Rocks at Various Geologic (Tectonic) Settings

Metamorphic Rocks TAKES ALREADY FORMED ROCKS AND CHANGES THEM – CAUSED BY INCREASED HEAT AND PRESSURE

Definition Metamorphism- changes in the mineral assemblage and textures of igneous, sedimentary or other metamorphic rocks due to prolonged exposure to elevated temperatures and pressures (or increased grades of metamorphism)

Types of Metamorphism 1) Contact metamorphism - High temperatures from surrounding to igneous intrusions- bodies of magma in the earth

Types of Metamorphism 2) High-pressure metamorphism – Forms because of gigh pressures at convergent plate boundaries boundary zones.

Types of Metamorphism 3) Regional metamorphism -Variable T, mod-high differential P; characteristic of over-thickened plates (i.e., mountain belts) above convergent boundaries; affects large areas

Why do we see high grade metamorphic rocks at the earth’s surface? Isostatic Rebound “Rapid” erosion of mountain belts of “dry” rocks

Textural Response to Metamorphism Reflects the intensity and directionality of pressure (or stress). Increased grain size - During prograde metamorphism or at a particular grade that is maintained for a long period of time, minerals will tend to increase in size. Foliation - As new platy minerals grow, they will align themselves perpendicular to the maximum stress direction. For clay mineral and fine-grained micas, the planar fabric that results is referred to as a slaty cleavage. In higher grade rocks, coarser grained mica minerals are said to impart a schistosity to the rock. Gneissic Banding - In very high grade rocks, the dark minerals tend to segregate from the lighter colored minerals (feldspar and quartz) resulting in banded rock..

Summary of Metamorphic Rock Types

Sedimentary Rocks THINK SEDIMENT LIKE LITTLE PARTICLES OF ROCKS AND MINERALS ALL PILED UP (DEPOSITED), SQUISHED (COMPACTED) AND GLUED TOGETHER (CEMENTATION)

Sedimentary Rocks SEDIMENTARY ROCK - Compacted and cemented accumulations of sediment, which can be of two general types - clastic and chemical. Clastic - composed of fragments of pre-existing rock that have been weathered, eroded and transported by wind, water, ice, or mass movement to a site of deposition. Chemical -composed of minerals precipitated from water due to evaporation or to bodily processes of of organisms.

Clastic Sedimentary Rocks Composed of fragments of pre-existing rock that have been weathered, eroded, and transported

Environments of Chemical Sedimentation Evaporites Coal Limestone

What Tectonic Settings Cause This?