Earth ScienceEarth Science

Branches of Earth Branches of Earth ScienceScience•GeologyGeology

•Meteorology Meteorology

•OceanographyOceanography

•AstronomyAstronomy

Geology Geology

•Study of the solid earthStudy of the solid earth

•Gives insight to the history of Gives insight to the history of the Earth (Paleontology)the Earth (Paleontology)

•Includes surface process which Includes surface process which have shaped the earth's surfacehave shaped the earth's surface

•Interior of the EarthInterior of the Earth

Continental Drift TheoryContinental Drift Theory

• Continental driftContinental drift is the movement  is the movement of the Earth's continents relative to of the Earth's continents relative to each other by appearing to drift each other by appearing to drift across the ocean bed.across the ocean bed.

•   First put forward by Abraham First put forward by Abraham Ortelius in 1596Ortelius in 1596

• Fully developed by Alfred Wegener in Fully developed by Alfred Wegener in 19121912

Alfred Lothar WegenerAlfred Lothar Wegener

  (Nov 1, 1880 – Nov 1930) (Nov 1, 1880 – Nov 1930)

• He was a German polar He was a German polar

researcher, geophysicist, and researcher, geophysicist, and a meteorologist.a meteorologist.

• he is most remembered for advancing he is most remembered for advancing the theory of the theory of continental driftcontinental drift  in 1912,  in 1912, which hypothesized that which hypothesized that the continents were slowly drifting the continents were slowly drifting around the Earth.around the Earth.

Evidences that continent Evidences that continent “drift”“drift”

Plate Tectonic TheoryPlate Tectonic Theory• Plate tectonics Plate tectonics (from the Late Latin (from the Late Latin

  tectonicustectonicus, from , from the Greek: τεκτονικός "pertaining to the Greek: τεκτονικός "pertaining to building") is a scientific theory that building") is a scientific theory that describes the large-scale motions describes the large-scale motions of Earth's lithosphere.of Earth's lithosphere.

•   The lithosphere is broken up into tectonic The lithosphere is broken up into tectonic plates. On Earth, there are seven major plates. On Earth, there are seven major plates and many minor plates.plates and many minor plates.

7 Major Plates on Earth7 Major Plates on Earth• PacificPacific

• North AmericanNorth American

• South AmericanSouth American

• AfricanAfrican

• EurasianEurasian

• AntarcticAntarctic

• Indo-AustralianIndo-Australian

Forces in Earth's CrustForces in Earth's Crust

•The movement of Earth's plates The movement of Earth's plates creates enormous forces that creates enormous forces that squeeze or pull the rock in the crust. squeeze or pull the rock in the crust. A force that acts on rock to change A force that acts on rock to change its shape or volume is its shape or volume is stressstress. Stress . Stress adds energy to the rock. The energy adds energy to the rock. The energy is stored in the rock until it changes is stored in the rock until it changes shape or breaks.shape or breaks.

Kinds of Stress:Kinds of Stress:

1.1.TensionTension pulls on the crust, pulls on the crust, stretching rock so that it stretching rock so that it becomes thinner in the middle.becomes thinner in the middle.

2.2.CompressionCompression squeezes rock squeezes rock until it folds or breaks. until it folds or breaks.

3.3.ShearingShearing pushes a mass of rock pushes a mass of rock in two opposite directions.in two opposite directions.

When enough stress builds When enough stress builds up in rock, the rock breaks, up in rock, the rock breaks, creating a fault. A creating a fault. A faultfault is a is a break in the rock of the break in the rock of the crust where rock surfaces crust where rock surfaces slip past each other.slip past each other.

Most faults occur along Most faults occur along plate boundaries, where plate boundaries, where the forces of plate motion the forces of plate motion push or pull the crust so push or pull the crust so much that the crust much that the crust breaks.breaks.

Where plates meet, their relative Where plates meet, their relative motion determines the types of motion determines the types of boundary: boundary: 

•Convergent boundaries Convergent boundaries where two where two plates approach each other, and one plate plates approach each other, and one plate

is subducted beneath anotheris subducted beneath another, , 

•Divergent boundaries Divergent boundaries where plates where plates move apart as new crust is formed (Mid-move apart as new crust is formed (Mid-

ocean ridges)ocean ridges), , •  Transform boundaries Transform boundaries where two where two

plates slide horizontally past each other on plates slide horizontally past each other on either side of a transform fault. either side of a transform fault. 

Types of plate boundariesTypes of plate boundaries

Deformation of rock involves Deformation of rock involves changes in the shape and/or changes in the shape and/or volume of these substances. volume of these substances. Changes in shape and volume Changes in shape and volume occur when stress and strain occur when stress and strain causes rock to buckle and causes rock to buckle and fracture or crumple into fracture or crumple into folds. folds. 

•A A fold can be defined as a  can be defined as a bend in rock that is the bend in rock that is the response to compressional response to compressional forces. Folds are most visible forces. Folds are most visible in rocks that contain layering. in rocks that contain layering.

Types of Folds:Types of Folds:1. Monocline

This fold involves a slight bend in otherwise parallel layers of rock.

2. Anticline- is a convex up fold in rock that resembles an arch like structure with the rock beds (or limbs) dipping way from the center of the structure

3. Syncline- is a fold where the rock layers are warped downward. Both anticlines and synclines are the result of compressional stress.

Synclinal folds in bedrock, near Saint-Godard-de-Lejeune, Canada. Synclinal folds in bedrock, near Saint-Godard-de-Lejeune, Canada. (Source: (Source: Natural Resources Canada - Terrain Sciences Division - Natural Resources Canada - Terrain Sciences Division - Canadian LandscapesCanadian Landscapes).).

4. Recumbent-develops if the center of the fold moves from being once vertical to a horizontal position.

Extreme stress and pressure can Extreme stress and pressure can sometimes cause the rocks to shear sometimes cause the rocks to shear along a plane of weakness creating along a plane of weakness creating a a faultfault..

FaultsFaults form in rocks when the stresses  form in rocks when the stresses overcome the internal strength of the overcome the internal strength of the rock resulting in a fracture. A fault can rock resulting in a fracture. A fault can be defined as the displacement of be defined as the displacement of once connected blocks of rock along once connected blocks of rock along a a fault planefault plane. . 

Types of Fault:Types of Fault:1. 1. Normal faultsNormal faults occur when tensional  occur when tensional forces act in opposite directions and forces act in opposite directions and cause one slab of the rock to be cause one slab of the rock to be displaced up and the other slab down.displaced up and the other slab down.

2. 2. Reverse faultsReverse faults develop when  develop when compressional forces exist compressional forces exist compression causes one block to be compression causes one block to be pushed up and over the other block.pushed up and over the other block.

3. G3. Graben fault raben fault is produced when is produced when tensional stresses result in tensional stresses result in the the subsidencesubsidence of a block of rock. On a  of a block of rock. On a large scale these features are known large scale these features are known as Rift Valleys.as Rift Valleys.

4. H4. Horst faultorst fault is the development of  is the development of two two reverse faultsreverse faults causing a block  causing a block of rock to be pushed up.of rock to be pushed up.

5.  5.  Strike Strike slip slip or or transform transform faultfault are vertical are vertical in nature and are in nature and are produced where produced where the stresses are the stresses are exerted parallel to exerted parallel to each other.each other.