GEOLOGY Chapter 15

Agents of Metamorphism: Pressure (stress)

- Increases with depth - Confining pressure - stress/pressure imposed by the weight of an overlying material - equal in all directions - phase changes can occur A new mineral that is more stable under pressure, graphite > diamond

Metamorphic grade and index minerals

- Index minerals - minerals that indicate the degree of metamorphism - quartz - not useful **shale cannot be metamorphosed into quartzite

Agents of Metamorphism: Impact Metmorphism

- Occurs when meteorites strike earth's surface - produces high pressure, high temp quartz, and polymorphs (coescite and stishovite) - gulf of mexico/yucatan

Upwelling zones:

- are areas where water flows in a vertical direction - bring nutrients up from depth - occur near the equator to replace water displaced by winds blowing steadily from east to west - can by driven by density differences cause by temperature and salinity differences.

Rogue waves:

- by definition are more than twice the size of large waves - have been documented as high as 34 m (112 ft) - can be caused by constructive wave interference and by interaction of waves with strong currents. - can be caused by the focusing effect of some coastline or seafloor shapes - they are not rare, there is an average of 10 at any given time some where in the world

Agents of Metamorphism: Subduction Zone Metamorphism

- deformed segment is called an accretionary wedge - sediments along an active margin

Agents of Metamorphism: Chemically active fluids

- mainly water - aids in re-crystallization of existing minerals SOURCES OF FLUIDS - pore spaces of sedimentary rocks - fractures in igneous rocks

Metamorphic environments

- occur near tectonic plate boundaries - more common - In association with igneous activity

Agents of Metamorphism: Metamorphism Along Fault Zone

- occurs at depth and high temperatures - ductile flow pre-existing minerals from - mylonite: produces a rock similar to gneiss

Barrier Islands

- sand ridges that run parallel to the shoreline - they are named that because they serve as barriers for the mainland in hurricane situations - lagoons separate barrier islands from the mainland - They are dynamic; meaning they are constantly moving by erosion and deposition and the shape of the islands is always changing, so don't build a house on them.

How do beaches get sand?

-erosion of local rock - carbonate remains of marine organisms - sand stored seaward of surf zone - River sediment arriving at the ocean (largest sand source for most beaches)

Metamorphism forms at temps around:

250c and 850c

The average depth of the oceans is approximately:

4-5 km

Hurricane scale

5 categories based on wind speed of the hurricane. 3 and up is major.

If the distance between the troughs of two adjoining ocean waves or swells is 100 m, how deep - from the average ocean surface - would you have to be in order to not feel any effect of the waves?

50 m

How much of the Earth's surface is covered by oceans?

71%

How does the lithosphere beneath a passive margin differ from that beneath an abyssal plain?

Abyssal plain is a broad, relatively flat region of the ocean that lies at least 4.5 km below sea level. the lithosphere beneath a passive margin lack seismicity.

Agents of Metamorphism: Burial Metamorphism

Associated with very tick sedimentary strata - depth varies from one location to another depending on geothermal gradient - just piling sediment upwards

Fjords are features of emergent coastlines

False - because emergent coastlines often have bluffs, cliffs, and rocky shorelines - just like fjords! However, fjords are formed when an alpine glacier carves a deep valley to the sea, the glacier melts, and the sea level rises to fill the valley. This is an example of submergent coastline caused by sea-level rise.

Coastal plains form predominantly along active margins

False - coastal plains form along passive margins, typically where some combination of ongoing continental erosion causes a mantle of sediment to build up over millions of years over a slowly subsiding, trailing plate margin such as the southeastern U.S. coastline.

Metamorphic Textures: Foliated

Foliated - planar arrangement of minerals or structural features within a rock. From Low grade to high. Slate- phyllite- schist- gneiss

What are some coastal hazards?

Hurricanes Tsunamis - generated by sudden displacements in the seafloor (earthquakes). They actually get bigger and bigger as they get closer to shore. Rip Currents - narrow currents that flow straight out to sea through the surf zone. They are fed by water in the surf zone.

Agents of Metamorphism: Regional Metamorphism

Increase in temperature with depth due to geothermal gradient. - produces largest quantity of metamorphic rocks - found in convergent plate boundaries and mountain building

Coastal Man-made structures

Jetties Groins - they are the ones that keep sediment to one side of the beach and the other side is basically left with little sand. Also, the deposition is left on one side so therefore, it disrupts both deposition and erosion Seawall Dikes/Levees Breakwaters

Metamorphic Rocks

Metamorphism: to change form Is one that when preexisting rock, or protolith (the parent rock) undergoes a solid state change in response to the modification of its environment. this process is called metamorphism.

Metamorphic Textures: Lineation

Mineral lineation, if rod-shaped minerals are aligned parallel to one another

Metamorphic Textures: Non-foliated

Non-foliated - non-planar arrangement of minerals. Deformation is minimal but heat is high (cause by temp). Formed during contact metamorphism. Composed of minerals that are interlocking or mosaic like marble, quartzite.

How do the shelf and slope of an active continental margin differ from those of passive margin?

The tectonic setting of a coast plays a role in determining whether the coast has steep-sided mountain slopes or a broad plain that borders the sea. Along active margins, compression squeezes the crust and pushes it up, creating mountains (like the Andes). Along passive margins, the cooling and sinking of the lithosphere may create a broad coastal plain, a flatland that merges with the continental shift (such as at the Gulf Coast).

The majority of tidal force is from the moon

True - the sun is so distant that it accounts for only 46% of the tidal forces on Earth. The Moon, which has far less mass, exerts a greater force because of its proximity to Earth.

Beaches usually consist of sand grains because waves winnow out finer sediment and carry it to deeper water, and break larger pieces down to sand-grain size.

True - waves move sediment from beaches to the deep water and break large pieces down, so beaches usually consist of only sand-sized particles.

What are problems for sediment deposition?

Upstream dams - they cut off the river sand supply, cause severe beach erosion Long shore drift waves strike shoreline at an angle, and sediment moves parallel to the shore Sediment moves as waves wash up on the beach face and most are transported by long shore current in surf zone Man-made structures like jetties and groins Coastal nourishment

Storm Surge

a mound of water produced when a hurricane moves across a large body of water. Higher than normal sea level

What is a hazard

a situation that poses a level to threat life, health, property, or environment

What is a beach?

a strip of sediment, coasts can be rock, cliff-ed, mountanious

The abyssal plains

are submarine canyons dissect the continental shelves and slopes

Metamorphic Textures: Porphyroblastic

contains large grains surrounded by smaller grains

Circular surface currents in major ocean basins are called:

gyres

All seas

have salinity ranging between 1 and 4.1%

Tidal Reach

is a difference in elevation. It was larger in the past than it is today because the moon was much closer to the Earth then it is now.

In which of these settings would you find an accretionary prism?

near a convergent margin along a coastline

Neap Tide

relative cancelling out of gravitational forces; the forces don't combine which creates a low tide

Coral animals

secrete calcite shells, so the coral mounds are limestone

Texture

size, shape, and arrangement of grains within a rock.

Spring Tide

sun and moon gravitational forces combine creates a high tide

What is a risk

the potential of losing something of value against the potential to gain something of value

What type of depositional environment is a lagoon?

transitional

Hurricanes

tropical cyclone; accompanied by thunderstorms and a counterclockwise circulation of winds near the earth's surface.

Coastal processes

wave erosion effect meaning that one rock stays isolated in the beach, straight sandy beach, rocky beach, you can have a reef and beach, you have a wave motion near shore, bulging water of the tides by the moon, storm surge effects

Solid State Diffusion

when the repetition of the process of reheating to create metamorphic rocks leads to rearrangement of atoms within grains or to migration of atoms in and out of grains