Earth’s Structure core: solid center surrounded by molten layer, mostly iron and nickel; mantle: solid zone with hot, partly molten "plastic" upper layer known as asthenosphere; rich in iron, silicon, oxygen, & magnesium; crust: outermost thin layer, location of mineral resources & soil. lithosphere: solid crust and uppermost part of mantle. This layers is divided into several Tectonic Plates

Plate Tectonics “Ring of Fire”: Earthquakes & volcanoes are distributed mostly in bands along the Earth's surface. These bands correspond to tectonic plate boundaries.

Plate Tectonics Plate boundaries undersea mountain chains (diverging plate boundaries) deep sea trenches (converging boundaries)

Major Plates on Earth

What Drives Plate Tectonics? Heat escaping from core creates convection currents in the asthenosphere Where currents rise, plates are pulled apart (divergence)

Plate Tectonics Types of boundaries Divergent Boundaries: Convergent Boundaries: Transform Boundaries:

Divergent Plate Boundaries Plates moving apart due to rising magma below. New oceanic crust is formed Eruptions are all basaltic (non-explosive) Undersea mountain chain is created called a mid- ocean ridge Process widens existing oceans (i.e. Atlantic ocean), or creates new ones (Red Sea, Great Rift Valley in Africa)

Evidence of Sea Floor Spreading Youngest rock found at mid ocean rift. Periodic reversals of the polarity of the Earth’s magnetic fields. Mirror images of magnetic polarity on either side of rift.

Divergent Plate Boundaries Divergence splits up continents.

Divergent Plate Boundaries The Red Sea is a newly forming ocean The rift valleys in Africa are splitting it apart

Hydrothermal Vents at Divergent Boundaries

Convergent Plate Boundaries Plates moving towards each other. Denser, thinner plate is subducted beneath the other plate Subducted plate is melted and produces explosive volcanoes on upper plate Three Types: Ocean-Ocean collision Ocean-Continent collision Continent-Continent collision

Convergent Plate Boundaries

Ocean-Ocean Collisions Older, denser ocean plate gets subducted and melts Deep trench is formed by bending of down-going plate Chain of volcanic islands is formed on upper plate = Island Arc. Example: Japan All islands are approximately the same age Volcanoes are explosive due to sediments (silica-rich) which get subducted with ocean plate Volcanoes are tall and pointy

Ocean-Ocean Collisions Cont. Examples include all the volcanic islands in the Western Pacific Island chains are usually arc-shaped Mineral-rich hydrothermal deposits may occur

“Accretionary Wedge” forms when lots of sediment on subducting plate cannot be forced down, so it piles up in front of the upper plate Accretionary wedges are non-volcanic (mostly scrunched up sediment) Example: Barbados

Ocean-Continent Collisions Ocean crust gets subducted because it is denser and melts beneath continent Explosive volcanoes form on continental plate (silica-rich due to subducted sediment and melted continental crust) Volcanoes are approximately the same age and are tall and pointy Trench is formed off the coast Mt. Shasta

Ocean-Continent Collisions Cont. Cascades in Pacific Northwest Andes in S. America Hydrothermal mineral deposits often occur (gold in CA)

Ocean-Continent Collisions What about the Olympics and the mountains on Vancouver Island? Olympics are non- volcanic, and marine fossils are found in its tallest peaks Sedimentary layers are extremely folded Accretionary Wedge (like Barbados)

Continent-Continent Collisions Continental crust is too thick and not dense enough to subduct, so very tall mountains are produced Mountains are non-volcanic Himalayas are still rising Older examples: Alps Appalachians

Transform Plate Boundaries Fig.14–4c Plates slide in opposite directions past each other Transform faults occur usually this occurs between different segments of mid-ocean ridges No volcanic activity occurs along transform faults Earthquakes are common

Transform Plate Boundaries Cont. The San Andreas fault connects two diverging plate boundaries, and is one of the only continental transform faults. Bay Area S. Cal

Hot Spots Hawaii Not located at plate boundaries. Deep magma source stays stationary as plate moves over it. Hot Spots under Oceanic Plates produce a chain of volcanic islands which get older away from the hot spot (i.e. Hawaii)

Hot Spots Hot spots erupting through ocean crust erupt only basalt -Eruptions are non- explosive -Volcanoes are shield type (wide, non-pointy) Mauna Loa

Hot Spots Cont. Hot Spots underneath Continental crust produce flood basalts and calderas (i.e. Deccan Traps, Yellowstone) Hot spot can melt portions of the continental crust (silica-rich), creating a massive, explosive eruption which leaves a caldera (big hole) behind Hot spots can have very active hydrothermal circulation, which will produce metal ore deposits The stationary deep hot spot does not seem affected by convection in mantle, which moves the plates above it. Deccan Traps

Yellowstone Hot Spot and Caldera

Geothermal Resources

Surface Geologic Processes erosion: the process by which earth materials are transported from one location & deposited in other locations (forming sedimentary rocks) weathering: physical & chemical processes in which solid rock exposed at the earth's surface is changed to separate solid particles & dissolved material; weathering is responsible for the development of soils; streams are the most important agent of erosion.