Chapter 4 Section 3, 4. Deforming the Earth s Crust

Chapter 4 Section 3, 4 Deforming the Earth s Crust

Deformation The process by which the shape of a rock changes because of stress

Stress The amount of force per unit area on a given material

Compression stress that occurs when an object is squeezed

Shear Stress that occurs when forces act parallel to the surface, pushing in opposite directions,

Shear Stress that occurs when forces act parallel to the surface, pushing in opposite directions

Tension stress that occurs when an object is stretched

Deforming the Earth s Crust Rock layers bend and break when stress is placed on them!

REVIEW Stress that occurs when forces act to squeeze an object Look at he arrows. Which type of stress is being illustrated? Stress that occurs when forces act to stretch an object Stress that occurs when forces act parallel to the surface, pushing in opposite directions, producing cutting instead of compression or tension

Folding bending of rock layers because of stress in Earth s crust http://www.indiana.edu/~g103/g103/week9/buck.jpg

COMPREHENSION CHECK! Q: How do the forces of plate tectonics cause rock to deform? A: Compression can cause rocks to be pushed into mountain ranges as tectonic plates collide at convergent boundaries. Tension can pull rocks apart as tectonic plates separate at divergent boundaries.

CONCEPT REVIEW! Q: What is plate tectonics? A: Plate tectonics is the theory that explains how large pieces of the Earth s outermost layer, called tectonic plates, move and change shape.

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Boundary A place where tectonic plates touch

Convergent Boundary The boundary formed by the collision of two lithospheric plates Two plates come together Hyperlink to Convergent Boundary Animation

Convergent Boundary The boundary formed by the collision of two lithospheric plates Continental-Continental Boundaries

Convergent Boundary The boundary formed by the collision of two lithospheric plates Oceanic-Oceanic Boundaries

Convergent Boundary The boundary formed by the collision of two lithospheric plates Continental-Oceanic Boundaries

Subduction Zone Where two plates meet and one slides under the other

Transform Boundary The boundary between tectonic plates that are sliding past each other horizontally Hyperlink to Transform Boundary Animation

Transform Boundary The boundary between tectonic plates that are sliding past each other horizontally Hyperlink to Video 3:03 San Andreas Fault California, USA

Divergent Boundary The boundary between two tectonic plates that are moving away from each other, or separate Hyperlink to Divergent Boundary Animation

Divergent Boundary The boundary between two tectonic plates that are moving away from each other Hyperlink to Divergent Boundary 0:11

Mid-Ocean Ridge A long, undersea mountain chain that forms along the floor of the major oceans

Mid-Ocean Ridge A long, undersea mountain chain that forms along the floor of the major oceans http://www.platetectonics.com/book/page_8.asp http://en.wikipedia.org/wiki/mid-ocean_ridge

Fault A break in a body of rock along which one block slides relative to another

The blocks of crust on each side of a fault are called fault blocks.

Hanging Wall Footwall

Reverse Fault

Reverse Fault The hanging wall moves up relative to the footwall. These normally occur when tectonic forces cause compression that pushes rocks together. Hyperlink to Animation of Reverse Fault

Strike-Slip Fault

Strike-Slip Fault These faults form when opposing forces cause rock to break and move horizontally. Hyperlink to Animation of Strike-Slip Fault

Normal Fault

Normal Fault The hanging wall moves down relative to the footwall. Hyperlink to Animation of Normal Fault

Rift Zone A set of deep cracks that forms between two plates that are pulling away from each other The East African Rift is an active continental rift zone in eastern Africa. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates called the Somali Plate and the Nubian Plate, which are sub plates or protoplates. http://ajs-geo-blog.blogspot.com/2012/03/rift-valley.html

Rift Zone A set of deep cracks that forms between two plates that are pulling away from each other The actual rift between the North American tectonic plate and the Eurasian plate. Iceland is the only place where this is visible above water.

http://www.uwec.edu/jolhm/hawaii2005/day3/hiwebsite/fs11.htm Rift Zone A set of deep cracks that forms between two plates that are pulling away from each other Southwest Rift, Hawaii The rift was formed over time during eruption of Kilauea. Hot magma moved underground from the summit reservoir in to the rift zone and tore the crust apart.

http://www.uwec.edu/jolhm/hawaii2005/day3/hiwebsite/fs11.htm Rift Zone A set of deep cracks that forms between two plates that are pulling away from each other Southwest Rift Hawaii

http://www.hp1039.jishin.go.jp/eqchreng/figures/af1-2.jpg

Name each type of Fault http://media.tiscali.co.uk/images/feeds/hutchinson/ency/c00948.jpg

What type of fault is this?

COMPREHENSION CHECK! Q: How does the hanging wall in a normal fault move in relation to a reverse fault? A: In a normal fault, the hanging wall moves DOWN. In a reverse fault, the hanging wall moves UP.

When Plates Collide Land features that start as folds and faults can eventually become large mountain ranges. Mountains exist because tectonic plates are continually moving around and colliding with one another.

Uplift rising of regions of Earth s crust to higher elevations V E R T I C A L M O V E M E N

Subsidence the sinking of Earth s crust to lower elevations V E R T I C A L M O V E M E N

Subsidence the sinking of Earth s crust to lower elevations V E R T I C M O V E http://ga.water.usgs.gov/edu/gwsubside.html A L M E N http://www.earthscienceworld.org/images/search/results.html?keyword=subsidence T

http://www.windows2universe.org/earth/clim ate/geosphere_plate_tectonics.html

COMPREHENSION CHECK! Q: How do uplift and subsidence differ? A: Uplift is the rising of the Earth s crust to higher elevations. Subsidence is the sinking of the Earth s crust to lower elevations.

COMPREHENSION CHECK! Q: What are rift zones? How do they form? A: Rift zones are cracks that form where two plates are pulling away from each other. As they pull apart, stress builds and faults form along the rift zone.