Chapter 9

Describe plate tectonics.

The mid-oceanic ridges and subduction zones mark the edges of enormous, moving, lithospheric plates, sometimes called tectonic plates. The seven largest plates are named for the continents that ride atop them, with the exception of the Pacific plate. Many smaller plates fill the spaces between these 7 massive shells of rock.

What are the names of the largest plates?

Eurasian Plate, African Plate, Australian Plate, North American Plate, South American Plate, Pacific Plate, Antarctic Plate.

Jupiter's moon, Europa, is completely smooth because the processes that destroy mountains act much more quickly than the processes that build them.

mountain building endogenic processes act much faster than mountain destroying exogenic processes.

Exogenic (external origin)

processes are driven by the energy in sunlight. Sunlight causes air to move, water to be lifted into mountains, and ocean waves to rise. These moving fluids attack the solid surface, eroding it, carrying the broken pieces far away, and depositing them to fill low places in the landscape. In other words, exogenic forces are mountain destroying processes.

Landform

Any individual feature, or group of features, that are made from the planet's native rock.

What are uniformitarianism and catastrophism?

At the heart of the study of geomorphology lies the deeply held belief that the geomorphic processes we observe today have been active throughout the geologic history of our planet, and that physical laws, as we understand them, have been constant in time. Very short term measurements of erosion rates, weathering rates, plate tectonic motion, and so on, and then extrapolate backwards in geologic time to understand the long-term development of landforms. Geomorphology research is based on the premise that "the present is the key to the past." An older theory suggests that the major work of landform shaping is done in sudden, planetary-scale events, rather than forming through gradual, uniform change. This idea, with religious origins, is referred to as catastrophism. The concept applies only to planet-wide upheaval, not to smaller-scale events such as earthquakes and volcanic eruptions.

Why do different layers have different densities?

Because of cooling at the Earth's surface. The crust and upper mantle have hardened while the rest of the mantle remains semi-molten. Heavier density elements and minerals sink to the bottom and lighter ones float to the surface.

Describe the interior layers of Earth.

Core, mantle and crust (continental crust & oceanic crust).

Structure

Different mountains shape, location and composition of mountains

Think of some examples of landforms created by each of these forces.

Endogenic - Molten lava. Exogenic - Water and glacial erosions.

Compare endogenic and exogenic processes. Where does each get its energy?

Endogenic: Internal origin processes driven by the internal heat of the Earth causing radioactive decay of elements deep beneath the surface (mountain building). Endogenic gets it's energy from the internal heat of the Earth. Exogenic (external origin) processes are driven by the energy in sunlight. Sunlight causes air to move, water to be lifted into the mountains, and ocean waves to rise (mountain destroying). Exogenic gets it's energy from Sunlight.

Processes

Used to explain similarities and differences in mountains structure. Forces, actions and time that formed them.

What are felsic and mafic rocks?

Felsic Rocks: Class of igneous rock. High in silica (aluminum & oxygen) and have low melting points and densities. Many continental igneous rocks are felsic granite. Felsic magmas produce explosive eruptions. Mafic Rocks: Class of igneous rock. High in iron & magnesium. Have higher melting points and densities. Sea floor crust is mafic basalt. Mafic magmas produce gentler, high volume flows characterized by Hawaiian volcanoes.

Distinguish between igneous, sedimentary, and metamorphic rocks and give examples of each.

Igneous Rocks: The youngest. Forms when molten magma cools and solidifies. (i.e. Basalt & Granite) Two classes: Felsic and Mafic. Sedimentary Rocks: Forms when small bits of mineral & other material build into thick deposits. (i.e. sandstone, limestone & shale). It forms in horizontal layers that preserve fossil remains. Metamorphic Rocks: Form when igneous or sedimentary rocks are exposed to intense heat and pressure. (i.e. marble & gneiss)

What are the lithosphere and asthenosphere and where are they located?

Lithosphere - The upper mantle and entire crust hardened together due to Earth's cooling to form rigid layer. Produced the largest features at Earth's surface. About 80 km (50 miles) thick. Asthenosphere - Part of the mantle. Semi-molten allowing the lithosphere to slide over it.

What are mid-oceanic ridges, subduction zones, lithospheric plates, transform faults, deep ocean trenches, and sea-floor spreading?

Mid-oceanic ridges: Centers of sea-floor spreading. The upwelling of magma from the upper mantle solidifies in the continuous creation of new, basaltic, sea floor crust. This new crust is then carried away from the spreading centers by the moving lithosphere. Subduction Zones: The sea floor crust collides with continental margins where it dives down into the mantle to be re-melted at subduction zones. The oldest sea floor crust is found at the farthest distance from a mid-oceanic ridge. The oldest yet sampled, found in the western Pacific, formed 280 million years ago. Lithospheric plates: The mid-oceanic ridges and subduction zones mark the edges of enormous, moving, lithospheric plates, sometimes called tectonic plates. The seven largest plates are named for the continents that ride atop them, with the exception of the Pacific plate. Many smaller plates fill the spaces between these seven massive shells of rock. Transform Faults Deep Ocean Trenches: Sea-Floor spreading:

What is the Moho?

Mohorovicic disctoninuity. Discovered by analysis of seismic waves. Deeper under the mountain ranges and continental crust than under oceanic crust. It would be shorter to dig a hole to the Moho through oceanic crust than continental crust.

Compare oceanic and continental crust.

Oceanic crust: Dense 3.0 grams/cm sq. Younger than continental crust. Much thinner about 5 km (3 mi) thick. Mostly basalt. Continental crust: light 2.7 grams/cm sq. Very old. Mostly granite. Thick 40 km (25 miles)

Think of an example of a violation of the principle of uniformitarianism.

On Venus, for example, it appears that the entire planet was suddenly resurfaced in a cataclysmic event 250,000 years ago that erased all surface relief.

Endogenic (internal origin)

Processes are driven by the internal heat of the Earth, which in turn results from the radioactive decay of elements deep beneath the surface. This heat bubbles upward providing a huge driving force that bends, cracks, lifts, and moves Earth's rigid outer layer. Occasionally we see this rising energy empty directly onto the surface in the form of molten lava. Typically, endogenic forces are mountain building processes.

What is the difference between structure and process?

Structure refers to the mountain's shape, location and composition. Processes refer to the forces, actions and time that formed them.

Geomorphology

Studies the landforms that pattern Earth's surface and the processes that shape them.

What is geomorphology?

Studies the landforms that pattern Earth's surface and the processes that shape them. Landform refers to any individual feature, or group of features, that are made from the planet's native rock.

What spurred the development of the theory of plate tectonics and how was it confirmed?

The acquisition of data showing the surface topography beneath the world's oceans.