Faults Normal Reverse Strikeslip Normal Fault Tension force

Faults • Normal • Reverse • Strike-slip

Normal Fault (Tension force) Associated with divergent boundary.

Reverse Fault (Compression force) Associated with convergent boundary.

Strike-Slip Fault Associated with transform boundary.

Hot Spots • an area in the mantle from which heat rises as a thermal plume from deep in the Earth • Molten material rises in the center of a plate – Example is Hawaii. – Hotspot does not move. – Plate moves.

Hotspots Seamounts • Hotspot: Molten material rises in the center of a plate. – Example is Hawaii. – Hotspot does not move. – Plate moves.

Earth Structure and Form

Crust • Crust: Thin rocky outer layer of Earth. – Oceanic Crust: • About 7 km thick. • Rocks are much younger than the continental crust. – Continental Crust: • About 8 -75 km thick. • Mohorovicic discontinuity: Boundary between crust and mantle. – Known as “Moho”.

Mantle • Mantle: Solid rocky shell that extends to a depth of 2890 km. – Partially melted state. • Over 82 % of Earth’s volume.

Core • Core: Sphere in the center of Earth consists of iron and nickel. – Density is about 13 g/cm 3. – Source of magnetic field around Earth!

Earth’s Layers Defined by Physical Properties • Earth is divided into 5 layers based on physical properties: properties – Physical properties are: temperature, pressure, and density. 1. Lithosphere 2. Asthenosphere 3. Lower Mantle (Mesosphere) 4. Outer Core 5. Inner Core

Lithosphere and Asthenosphere • Lithosphere: Rigid outer most layer of Earth consists of the crust and upper mantle. • Asthenosphere: Highly viscous layer of the upper mantle. – Layer is weak because the temperature and pressure are just above melting point.

Lower Mantle • Lower mantle: Rigid layer that begins about 660 km below the surface. – Rocks are strong and capable of flowing. • Rocks are very hot (molten).

Inner and Outer Core • Core is composed of iron-nickel alloy. – Outer Core: Liquid layer is 2260 km thick. • Generates the Earth’s magnetic field. – Inner Core: Solid layer that is 1220 km thick. • Despite extremely high temperatures it is under immense pressure and is condensed into a solid.

Discovering Earth’s Layers • Seismic waves from earthquakes travel through the earth. – Velocity of seismic waves increases just below the crust and above the mantle known as the Mohorovicic discontinuity. • Shortened to Moho. – Example: Antarctica has records from earthquakes that occurred in California and Italy.

Mountain Building Chapter 11

Orogenesis • Orogenesis: Collection of geological processes that form mountains. – Literally means “mountain birth”. • Uplift: Upward movement of rocks through various geological processes.

Deformation • Deformation: Change in the size and shape of a rock caused by a stress. Stress: Force per unit area. • – Factors that deform rocks: 1. 2. 3. 4. Temperature Pressure Rock Type Time

Temperature and Pressure • Rocks deform in two ways: a) Brittle Deformation: Rocks changing shape by fracturing. • Rocks near the surface are under low amounts of heat and pressure. – Example: Glass fracturing or even bones fracturing. b) Ductile Deformation: Rocks changing shape without fracturing (stretch). • Rocks near high heat and pressure near the mantle and subduction zones. – Example – A penny being flattened by a train.

Rock Types a) Rocks like granite and basalt have strong molecular bonds. – Brittle deformation. – Example: Rocky Mountains, which are sharp mountains b) Rocks such as limestone have weak bonds. – Ductile deformation. – Example: Appalachian Mountains, which are gently flowing mountains.

Rock Types Rocky Mountains Appalachian Mountains

Time • Steady amounts of stress slowly make rocks “flow”. – Rocks may change shape essentially under their own weight. – Example: Marble benches under their own weight sag over the course of hundreds of years.

Types of Stress • Three types of stresses that rocks undergo: 1. Tensional Stress (Extensional) • Pulling away which causes mountain ranges and valleys. 2. Compressional Stress • Pushing inward towards each other creating a mountain range. 3. Shear Stress • Top is pulling one way and the bottom is pulling the opposite direction.

Tensional Stress • Tensional stress: Pulling away that produces mountain ranges and valleys. – Also known as extensional stress.

Compressional Stress • Compressional stress: Pushing inward towards each other creating a mountain range.

Shearing Stress • Shearing stress: Top is pulling one way and the bottom is pulling the opposite direction.

Folds • Folds: Series of wavelike ripples in rock layers. • Three main types of folds: 1. Anticlines 2. Synclines 3. Monoclines

Anticline • Anticlines: Caused by the upfolding or arching of rock layers.

Syncline • Synclines: Downward fold or troughs associated with anticlines.

syncline anticline

Monocline • Monoclines: Large step like fold associated with a fault.

Folded Mountains • Mountains that form from folding processes. – Compressional stress. – Examples: Appalachian and Alps

• Mountain Fold Video – 2. 2 minutes – Anticline and Syncline Information

Fault Block Mountains • Large blocks of rock are uplifted and tilted by normal faults. – Example: Grand Teton Mountains in Wyoming

Fault Block Mountains

• Fault Block Video – 1. 2 minutes

Volcanic Mountains • Formed by lava and pyroclastic material build up. – Example: Hawaii, Surtsey in 1963 Surtsey in 1999

Domes and Basins Domes: Occur where up -warping produces a circular or elongated arched structure. Basins: Occur where down-warped structures have a circular shape.

Horsts and Grabens • Horsts: Elongated, uplifted block of rock along a fault. • Grabens: Valley formed by the displacement by a block of rock along a fault.