Seafloor

Question 1

Geography of the ocean basins

Answer 1

Oceans cover 71% of earth in total area
- 61% northern hemisphere
-80% southern hemisphere

Question 2

Four ocean basins

Answer 2

Pacific
Atlantic
Indian
Arctic
(The oceans are interconnected as a single world ocean)

Question 3

Origin of earth

Answer 3

-4.5 billionths ago from dust accumulated form the bing bang
-Early earth was likely molten (hot)
-materials settled by density as they cooled
-Heaviest materials sunk to center of earth

Question 4

Density

Answer 4

Mass per unit volume

Question 5

Internal estructure of the earth

Answer 5

-Core: innermost layer, solid inner core and liquid outer core; iron-rich produces earth’s magnetic field
-Mantle: middle layer, semi-plastic (semi-solid) composition.
-Crust: outermost layer, thinnest portion of the Earth

Question 6

Oceanic crust

Answer 6

Dark-colored mineral material, basalt; denser than continental crust.
Younger mess than 200 millions years old.

Question 7

Continental crust

Answer 7

Light-colored mostly granite; less dense; some 3.8 billions years old

Question 8

Continental drift

Answer 8

-Alfred Wegner (1912)
-Movement of continental masses on the surface of earth.
-All continents had been joined in a single supercontinent, named Pangaea
-Pangaea began breaking up 180 MYA

Question 9

Plate tectonics

Answer 9

Movement of large plate on earth’s crust
- Explains continental drift

Question 10

Mid-Ocean ridges

Answer 10

-Chain of submarine volcanic mountains
- Ridge is displaced by faults in the Earth’s crust called transform faults.
- crust separates creating rifts, sea floor spreads away from the ridges.

Question 11

Significance of mid-ocean ridges

Answer 11

-geological activity is concentrated where plates meet
-earthquakes at ridges and volcanoes at trenches
-sea floor is young at the ridge and gets older as it moves away.

Question 12

Geomagnetic anomalies

Answer 12

-Earth’s magnetic field reverses periodically
-New rock formed from magma records the orientation of earth’s magnetic field at the time the magma colds
-Studies of the sea floor have revealed “stripes” of alternating magnetization parallel to the mid-ocean ridges.

Question 13

Lithosphere

Answer 13

Made up of tectonic plates and top portion of the mantle

Question 14

Ridges

Answer 14

Form edges of plates. Sea floor spreading and new sea floor is being created

Question 15

Slab pull

Answer 15

Causes plates to separate at the ridge

Question 16

Trenches

Answer 16

Depression in the sea floor

Question 17

Subduction

Answer 17

Occurs when one plate dips into the mantle under another plate, forms trenches.

Question 18

Island arcs

Answer 18

Are chains of volcanic island along trenches

Question 19

Geologic history and continental drift

Answer 19

-Pangea surrounded by Panthalassa
- Pangea separated into Laurasia and Gondwana
- Gondwana separated
- Atlantic Ocean grew
- Australia separated, India collied

Question 20

Marine sediments (two types)

Answer 20

Lithogenous sediments - derived from the break- down of rocks (weathering)
Biogenous sediments- derived from the skeletons and shells of marine organisms

Question 21

What can we learn from marine sediments?

Answer 21

-Earth’s climates has fluctuated rhythmically
- Interglacial periods (warm): sea level rises
-Ice ages (glaciers build up): sea level falls as water is trapped in ice on continents
-Human influence intensifies the greenhouse effect
- sea level projected to rise next century

Question 22

Continental margins

Answer 22

Are boundaries between continental crust abs oceanic crust
- continental shelf (most landward)
-continental slope
Continental rise (most seaward)

Question 23

Continental shelf

Answer 23

• Makes up 8% of the ocean’s surface area
• Richest area of the ocean (number of species)
  -It’s width varies from 1 km to 750 km
• the shelf ends when the shelf break

Question 24

Continental slope

Answer 24

-Edge of a continent
- Begins as the shelf break and extends to the deep sea floor
-Steepest part of the continental margin

Question 25

Continental rise

Answer 25

• formed by a thick layer is sentiment piled on sea floor
  -sediments that have been pushed down from the continental shelf and slope

Question 26

Abyssal plain: Deep ocean basins

Answer 26

Most of deep-sea floor (abyssal plain)
-Numerous seamounts - submarine volcanoes
- flat-topped sediments called guyots common
-great biodiversity
-the deepest part of the world
-Mariana trench is deepest in the world 10,994 m (36,070 ft)

Question 27

Hawaiian island formations

Answer 27

-Are a chain of seamounts
-form over a hot spot, a plume of magma rising from deep in the mantle
-tectonic plate moves over the stationary hotspot.

Question 28

Hydrothermal vents

Answer 28

-Sea water seeps into cracks in the crust and rises in hydrothermal vents.
-Water can be as hot as 350 C (660) F
-Hot water cools quickly, dissolved .sulfide minerals solidify into deposits called black smokers.