Origin of the Oceans

Question 1

the earth surface can move in three ways?

Answer 1

1) Divergent Motion: When two tectonic plates
move apart from one another.
2) Convergent Motion: When two tectonic plates
move toward one another.
3) Transform or ‘strike slip’ Motion: When two
tectonic plates slide past one another at an angle.

Question 2

mid Atlantic ridge

Answer 2

east pacific rise

Question 3

convergent ocean to continental

Answer 3

Subducting Nazca plate

Question 4

The process of tectonic subduction occurs

Answer 4

when two tectonic plates convergent together.

Question 5

Continental Crust

Answer 5

Continental crust is made of lower density
minerals.
Continental crust is thick (60-100 km)
Continental crust is very old
New continental crust is very rare

Question 6

Oceanic Crust

Answer 6

Oceanic crust is made of higher density
minerals
Oceanic crust is rather young in age
Oceanic crust is thin (7-10 km)

Question 7

Types of Continental Margins

Answer 7

PassivePassive
 Not on plate boundaries
 Lack active volcanoes & earthquakes
 Active Type
 On plate boundaries
 Active volcanoes & earthquakesActive volcanoes

Question 8

Features of Passive,Continental Margins

Answer 8

 Continental Shelf
 Continental Slope
 Continental Rise

Question 9

Features of the Continental Shelf

Answer 9

Average Depth = 133 Meters (440 ft)
 Maximum Depth= 200 meters (660 ft)
 Average width == 78 km (50 mi)
 Range of Width == 0 to 1500 km (950mi)
 Sea ward slope == 0.1 degree
 Amount above sea level can vary greatly

Question 10

Continental Margins are good
sediment traps sediments
collect there?

Answer 10

Lithogenous , Gravel, sand, silt, clay
Biogenous, Shells, bone, teeth, droppings
Hydrogenous,Chemical precipitates - lime, salt, sulfides

Question 11

Active ContinentalMargins,Associated with Divergent Plate Boundaries

Answer 11

Young narrow seas with continental slopes
and shelves (example = Red Sea)
Become passive continental margins as sea
floor spreading continues.

Question 12

Active ContinentalMargins,Associated with Transform Boundaries

Answer 12

1,Continental Borderlands
2,Alternating up-thrown and down-dropped fault blocks.
3, Often expressed as islands and basin.

Question 13

Active Continental Margins.
Associated with Convergent Boundaries.

Answer 13

Deep Ocean Trenches.
 Island Arcs
 Subduction Zones
 Active continental mountain ranges

Question 14

Island Arcs

Answer 14

Arcuate chains of islands, separated from continents by a marginal sea

Question 15

Ocean Sediment Types

Answer 15

Lithogenous, Gravel, sand, silt, clay
Biogenous, Shells, bone, teeth, droppings
Ooze = sediment with over 30% biogenic material
Hydrogenous, Chemical precipitates - lime, salt, sulfides

Question 16

Active Continental Margins

Answer 16

Associated with Divergent Plate Boundaries.
Young narrow seas with continental slopes and shelves (example = Red Sea)
-Become passive continental margins as sea floor spreading continues.

Question 17

Active Continental Margins
Associated with Transform Boundaries

Answer 17

Continental Borderlands
 Alternating up-thrown and down-dropped fault blocks.
 Often expressed as islands and and basins.

Question 18

Active Continental Margins
 Associated with Convergent Boundaries

Answer 18

Deep Ocean Trenches
 Island Arcs
 Subduction Zones
 Active continental mountain ranges

Question 19

Examples,Trenches

Answer 19

 Kurile Trench
 Marianas Trench -Deepest - 11,035 meters
 Aleutian Trench
 Peru-Chile Trench - Longest - 5900km
 Tonga- Kermadec Trench
 Puerto RicoTrench

Question 20

Deep Sea Sediments

Answer 20

Accumulate very slowly
Ø 1 to 15 millimeters per year
Ø (1/2 inch per year)

Question 21

Abyssal Plains

Answer 21

Relatively flat floors of ocean basins
Ø Thin veneer of deep sea sediment
l Generally about 500 meters (1500 ft) thick
 Basaltic oceanic crust underlies sediment
l Often pillow basalt lava
1 to 2 km thick
 Lower crustal layer is gabbro plutons
3 to 6 km thick

Question 22

Why Study Deep Sea Sediments

Answer 22

 Climate change
 Benthic habitats
 Off-shore pollution
 Sources of dredged material
 Sources of off-shore minerals
 Understand ocean floor topography
 Understand Earth’s different
environments