Ocean Geology

What is a Convergent Boundary?

Plates moving towards/colliding each other

What forms at a Convergent Boundary?

Island Arcs and/or Volcanic Mountain Chains

Which plate subducts?

Convergent

What is subduction?

When trenches from as a result of a heavier plate moving under a lighter one

What do convergent boundaries do to the lithosphere?

Subduction

What are transform boundaries?

Plates that slide past one another

Famous example of an active transform boundary

San Andreas Fault, CA

What are divergent boundaries?

Plates that move apart from one another

What do divergent boundaries do to the lithosphere?

Creates a new crust / mid-ocean ridges / make islands

What are manganic anomalies?

Altering bands in the ocean crust that shows the magnetic field of when the rock was formed

What’s Paleomagnetism?

Magnetic records in ancient rock

Which boundary is most likely to create tsunamis?

Convergent Boundaries

What are hydrothermal vents?

Underwater geysers (deep-sea hot springs) that are found along the mid-ocean ridge’s Rift Valley

How do hydrothermal vents form?

Seawater seeping into cracks in Rift Valley, which is heated up by rising magma, causing water to rise through the crust

What starts the food chain at hydrothermal vents?

Chemosynthetic bacteria and archaea

What is at the top of the food chain at hydrothermal vents?

Vent Crabs

How deep is the Abyssal Plain?

3000-5000 meters (10,000-16,500 feet)

What is a guyot?

Flat topped seamount

What is a seamount?

Underwater mountain

What is an island?

A landmass that is surrounded by water; is formed when the top of the volcano reaches the surface

What are the 4 oceans?

• Atlantic

• Pacific

• Indian

• Southern

How much of the southern hemisphere is ocean?

80%

How much of the plant is covered in ocean?

70%

What are Continental Margins?

Boundaries between the continental crust and the ocean; submerged edge of continents

What is a continental self?

The part of the continent that is underwater

What is the shelf break?

The underwater edge of a continental shelf, where it begins a rapid slope to the deep ocean floor; the drop off

What is the continental slope?

The steep area between the continental shelf and the deep ocean floor, transitioning from shallow to deep waters; begins at 120 to 200 meters (400 to 600 feet)

What is the continental rise?

The thick layer of sediment on the sea floor at the base of the slope

What are deep sea fans?

Sedimentary deposits formed at the base of continental slopes; formed by the accumulated sediments transported by underwater currents

How was Hawaii form?

By the Pacific plate movign over a hot spot

What is a hot spot?

A mantle plume that’s in the middle of a plate

What is a plume?

A column of one fluid moving through another

What is the ring of fire?

A string of volcanoes and sites of earthquake activity; located around the edges of the Pacific Ocean

What are active margins?

Occurring at the edge of converging plates, they’re very active with trenches offshore, no rises, narrow shelves, and steep rock slopes.

What’s an example of a active margin?

The California Coast Line

What are passive margins?

Occurring at the edge of continental crust within a plate, they’re geologically inactive, with flat coastal plains, wide continental shelves, and more gradual slopes

What’s an example of a passive margin?

The East Coast of North Carolina

What the physical layers of the Earth?

• Crust

• Mantle

• Core

Crust

The outermost layer of the Earth; top part of the lithosphere; made of hard and brittle rock

Oceanic Crust

A younger, thinner, and more dense crust. Subducts with the continental crust

Continental Crust

A older and less dense crust

What are the chemical layers of the Earth?

• Lithosphere

• Asthenosphere

• Outer Core

• Inner Core

Lithosphere

pullsComprised of the crust and upper mantle; pull along the Asthenosphere

Asthenosphere

The middle layer of the mantle; molten and putty-like; has convection currents; located between the upper and lower mantle

Outer Core

Molten layer under the lower mantle

Inner Core

Solid later inside the outer core; spins within the outer core; creates Earth’s magnetic field

When and how was the Mid-Ocean Ridge discovered?

By SONOR after World War 2

Where are trenches most commonly found?

In the Pacific Ocean

Age of Ridges near the center

Geologically young

Age of Ridge far from the center

Geologically old

Sediment in RIdges

Very little exist near the center; amount of sediment increases with distance from the center; sediment farther away is very old

How many years does it take for the magnetic field to reverse?

Every 5000 years

Types of Ocean Sediment

• Lithogenous

• Biogenous

What is lithogenous sediment?

Made from eroded rocks; red clay

What is biogenous sediment?

Made from skeletons and shells of marine organism; calcareous ooze and siliceous ooze; gives us clues about changes in temperature