Geologi Laut Deep Sea Observation

Deepsea geology and submarine volcanoes

The Continental drift theory

Plate tectonics model

Deep ocean geo-survey

Glomar Challengers survey

Great findings:

fluids circulating through the ocean floor;

the formation of gigantic volcanic plateaus at phenomenal rates unknown today;

natural methane frozen deep within marine sediments as gas hydrate;

a microbial community living deep within oceanic crust;

climate change cycles

Magnetic survey

Findings:

Two or three times every million years, Earths geomagnetic fieldreverses polarity, with the north and south magnetic poles switching places.

Over the last 4 million years, the field reversed 11 times. Over the last 170 million years, Earths magnetic field has reversed 300 times.

Magnetic survey (cont...)

Alvin (1960s)

Findings:Black smoke around GalapagosRMS Titanic observations

Satellite imagery

Geoid height= difference between the height above the ellipsoid and the altitude above the ocean surface is approximately equal to -> N = h* - h.

Prediction ocean depth Plate tectonics Seafloor volcanoes Petroleum survey

Dynamic of seafloor: Oceanic crust

Oceanic crust primarily composed of mafic rocks, rch of iron and magnesium [basalt, coming from inner earth].

Lesser than continental crust (

Oceanic crust (cont...)

Seafloor spreading

Seafloor Spreading is the usual process at work at divergent plate boundaries, leading to the creation of new ocean floor.

begins with hot rock rising from deeper portions of the mantle by

convection currents. After reaching the underside of the lithosphere, the mantle

rock spreads out laterally, dissipates heat near the surface, cools, and

descends back into the deep interior of the Earth, where it receives more heat

in a repeated cycle.

Mid Ocean Ridge

Center of oceanic crust activity Range about 1000 miles north of Antartica to Iceland Extensive volcanism gives rise to volcanic islands such as

Surtsey The submerged mountains and undersea ridges form a

continuous chain 46,000 miles long. (longest mountain range in the world)

Ring of Fire

Plate subduction is responsible for the intense seismic activity that fringes the Pacific

An inner belt runs parallel to the main belt and takes in the Marianas, characterized by a massive trench system in places more than 30,000 feet deep

Ocean in a region known as the circum-Pacific belt, a chain of subduction, zones flanking the Pacific basin.

The Ring of Fire is an area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean.

As a direct result of plate tectonics movement and collisions of lithospheric plates

The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes.

Indonesias volcanoes are most active among ring of fire

Remember....

Southeast Asia Cenozoic Paleogeographic Evolution

0 ma

Present day

Mod. from Scotese and PALEOMAP (2005)


60 ma

Paleocene


50 ma

Early Eocene


40 ma

Late Eocene


30 ma

Oligocene


20 ma

Early Miocene


10 ma

Late Miocene


0 ma

Present day

Seamounts and guyots

Seamounts are individual volcanoes on the ocean floor. They are distinct from the plate-boundary volcanic system of the mid-ocean ridges, because seamounts tend to be circular or conical.

Large seamounts are often fed by "hot spots" in the deep mantle. Melting of sediment in the subduction zones as a source of new molten magma Convective motions in the wedge of asthenosphere caught between the descending oceanic plate and

the continental plate force material upward, where it melts under reduced pressures. The magma rises to the surface in giant blobs called diapirs. Upon reaching the underside of the lithosphere, the diapers burn holes through the crust as the molten

rock melts on its journey upward. As the diapirs rise toward the surface, they form magma bodies, which become the immediate source

for new igneous activity. After reaching the surface, the magma erupts on the ocean floor to create new volcanic islands strung out on the ocean floor along with other volcanic activities

Seamount vs Guyots

Guyots (1-3) are seamounts that have built above sea level. Erosion by waves destroyed the top of the seamount

resulting in a flattened shape. Due to the movement of the ocean floor away from

oceanic ridges, the sea floor gradually sinks and the flattened guyots are submerged to become undersea flat-topped peaks.

Guyots contain evidence of fossils such as coral reefs that only live in shallow water.

Seamounts (4) conversely represent volcanoes that did not reach sea level so their tops remain intact and are shaped like volcanoes on land.

Island arcs

An island arc is a type of archipelago, often composed of a chain of volcanoes, with arc-shaped alignment, situated parallel and close to a boundary between two converging tectonic plates.

Most of these island arcs are formed as one oceanic oceanic plate, subducts another one and, in most cases, produces magma at depth below the over-riding plate.

i.e: Sunda islands (Indonesia), at basin Java Sea, Overriding by Eurasian plate, subducting Australian plate

Rift volcanoes

Rift volcanoes form when magma rises into the gap between diverging plates.

They thus occur at or near actual plate boundaries

Hot spot volcanoes

Isolated from plate boundaries

As oceanic volcanoes move away from the hot spot, they cool and subside, producing older islands, atolls, and seamounts.

As continental volcanoes move away from the hot spot, they cool, subside, and become extinct

Difference among them..Su

bd

uct

ion

vo

lcan

oes occur where plates move towards each

other and collide(subduction zone)

Subduction zone:

Ocean-continent

Ocean-ocean

Continen-continent Rif

t vo

lcan

oes Occur where plates are moving apart,

as in the middle of the Atlantic Ocean

magma rises through the gap between the separating plates and creates new rock

erupt more gently than other types of volcano

Ho

tsp

ot

volc

ano

es found away from the edges of the plates

formed where rising plumes of magma force their way to the surface from deep within the mantle, a hot spot

Hydrothermal vents

Hot springs on the ocean floor are called hydrothermal vents. The most numerous and spectacular hydrothermal vents are found along worlds mid-ocean ridges.

The heat source for these springs is the magma (molten rock) beneath the volcanic ridge system.

Velocities of 1-5 m/sec and at temperatures of 200-400 C (400-750 F)

The precipitate includes iron, gold, silver, copper, zinc, cadmium, manganese, and sulfur, along with significant amounts of methane gas mixed into the fluid. Halides, sulphates, chromates, molybdates and tungstates

Patented: Marshall tech hydrothermal system

Fin.....

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Geologi Laut Deep Sea Observation