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 Pull Mantle Push

Types of Plate Boundaries

Divergent Plate Boundaries

Mid-ocean RidgesWhere Oceanic Crust is

Made!

Youthful Oceanic Crust

Basalt – Rock Typeof the OceanicCrust

Remember:Melting the mantle makesmafic magma!! Always

Continental Rifting The creationof new ocean basins

Horst and Horst and Graben FormationGraben Formation

Convergent Boundaries

Ancient Continental Crust

Convergent Boundaries- Where the Action Is!!

Ocean-Continent

Continent - Continent

Ocean - Ocean

Earthquakes

Volcanoes

Mt. St. HelensMay 18, 1980

Consequences of ConvergenceExplosive Volcanism

Consequences of ConvergenceMountain Building & Rock Deformation

Consequences of ConvergenceEarthquakes

Banda Ache, Dec. 26, 2004

OROGENESIS

The Culmination

of Convergence

San Francisco EarthquakeApril 18, 1906 Mag 7.8Transform

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 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 Fine-grained = Volcanic= Volcanic

Coarse-grained Coarse-grained = Plutonic= Plutonic

Igneous Environments

Creation of Igneous Rocks at Various Geologic (Tectonic) Creation of Igneous Rocks at Various Geologic (Tectonic) SettingsSettings

Metamorphic Rocks

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

PRESSURE

DefinitionMetamorphism- 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 Metamorphism1) Contact metamorphism - High temperatures

from surrounding to igneous intrusions- bodies of magma in the earth

Types of Metamorphism2) High-pressure metamorphism – Forms

because of gigh pressures at convergent plate boundaries boundary zones.

Types of Metamorphism3) 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 MetamorphismReflects 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 RocksComposed 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?