1. Program Studi Ilmu Kelautan
GEOLOGI LAUT
MORFOLOGI DASAR LAUT
FIGURE (A) Coral reefs form abundantly in clear, shallow, tropical water.This small island on the east coast of
Australia is surrounded by reefs that are part of the Great Barrier Reef.
Program Studi Ilmu Kelautan
FMIPA UNSRI
Fig a, p.423

2. Topograpi dasar laut??
Bentuk2, pola dan konfigurasi fisik permukaan dasar laut.
Kenampakan dasar laut: Kombinasi aktivitas tektonik dan the processes of erosion and deposition.

3. Dasar Laut Oceans = 71% of the Earth’s surface.
Belahan bumi utara: 60% laut, 40% daratan
Belahan bumi selatan: 83% laut, 17% daratan.
Four main ocean basins:
 Pacific,
 Atlantic,
 Indian, and
 Arctic
Laut Pacific  Laut paling luas dan paling dalam (average depth ~4,000 meters)

4. Ocean Basins
Arctic Ocean

5. Bathymetry: Peta dasar laut :
Echo sounding
Multibeam Systems
Satellite Altimetry

6. Echo sounding :
Measured depth equals true depth
True depth immediately beneath vessel
Sound beam emitted by echo sounder (beam angle is exaggerated)
Measured depth is less than actual depth
Figure 4.2
(a) The accuracy of an echo sounder can be affected by water conditions and bottom contours. The pulses of sound energy, or “pings,” from the sounder spread out in a narrow cone as they travel from the ship. When depth is great, the sounds reflect from a large area of seabed. Because the first sound of the returning echo is used to sense depth, measurements over deep depressions are often inaccurate. (See Figure 2.24 for a review of echo sounding.)
Seafloor
Fig. 4-2a, p. 79

7. Echo-sounding: menggambarkan topografi dasar laut

8. Multibeam Systems: Kombinasi banyak echo sounder
Figure 4.3
(a) The accuracy of an echo sounder can be affected by water conditions and bottom contours. The pulses of sound energy, or “pings,” from the sounder spread out in a narrow cone as they travel from the ship. When depth is great, the sounds reflect from a large area of seabed. Because the first sound of the returning echo is used to sense depth, measurements over deep depressions are often inaccurate. (See Figure 2.24 for a review of echo sounding.) (b) An echo sounder trace. A sound pulse from a ship is reflected off the seabed and returns to the ship. Transit time provides a measure of depth. For example, it takes about 2 seconds for a sound pulse to strike the bottom and return to the ship when water depth is 1,500 meters (4,900 feet). Bottom contours are revealed as the ship sails a steady course. In this trace, the horizontal axis represents the course of the ship, and the vertical axis represents water depth. The ship has sailed over a small submarine canyon.
Multibeam systems : dpt memberikan hasil pengukuran yg lebih akurat. Menggunakan 121 beams radiating from a ship’s hull. Beam ini dapat mengkover sudut 120°

9. Satellites: Dpt digunakan untuk pemetaan kontur dasar laut
Menggunakan satellite altimetry, sea surface levels dapat diukur lebih akurat,
Figure 4.4
(a) Geosat, a U.S. Navy satellite that operated from 1985 through 1990, provided measurements of sea surface height from orbit. Moving above the ocean surface at 7 kilometers (4 miles) a second, Geosat bounced 1,000 pulses of radar energy off the ocean every second. Height accuracy was within 0.03 meter (1 inch)! Other satellites have taken its place. (b) Distortion of the sea surface above a seabed feature occurs when the extra gravitational attraction of the feature “pulls” water toward it from the sides, forming a mound of water over itself.

10. Topografi dasar laut bervariasi menurut lokasi
Cross sections Atlantic Ocean basin dan the continental United States, menunjukkan range elevasi. Skala vertical exaggeration: 100:1.
Although ocean depth is clearly greater than the average height of the continent, the general range of contours is similar.
Figure 4.5
Cross sections of the Atlantic Ocean basin and the continental United States, showing the range of elevations. The vertical exaggeration is 100:1. Although ocean depth is clearly greater than the average height of the continent, the general range of contours is similar.

11. Struktur Dasar Laut Continental Margin : Continental Shelf
(near continent) Continental Slope
Continental Rise
Submarine Canyons
Continental Margins – Bagian sisi benua yang terdapat di bawah permukaan laut
Passive margins, disebut Atlantic-type margins, face the edges of diverging tectonic plates. Sangat sedikit/no aktivitas volcanic atau gempabumi yg terdapat pada daerah ini.
Active margins, known as Pacific-type margins, terletak dekat sisi converging plates. Active margins tempat aktivitas vulkanik atau gempa bumi.
2. Deep Ocean Basin : Abyssal Plains
Oceanic ridges
3. Lain2: a Trenches
b Seamounts and Guyots
c Atolls

12. 2. Deep Ocean Basin : Abyssal Plains
Oceanic ridges
3. Lain2: a Trenches
b Seamounts and Guyots
c Atolls

13. Figure 4.9
The features of a passive continental margin. (a) Vertical exaggeration 50:1. (b) With no vertical exaggeration.

14. Continental slope
Continental shelf
Continental
Shelf
Volcanic island
Seamount
Continental slope
Abyssal plain
Continental rise
trench
mid-ocean ridge
Rift valley

15. Kenampakan Utama

16. Kenampakan Dasar Laut
Flat-topped seamounts eroded by wave action are called guyots.
Abyssal hills are small, extinct volcanoes or rock intrusions near the oceanic ridges.

17. Continental Margins Passive Active
Passive continental margins mempunyai continental shelf, continental slope, and continental rise descending to the abyssal plain
Active continental margins have continental shelves and slopes, but the slope extends down into a deep oceanic trench
A mid-oceanic ridge system encircles the globe, typically running down the center of oceans
Banyak gunung laut yang berbentuk kerucut rise from the deep ocean floor

18. Continental margin
Deep-ocean basin
Submarine canyon profile (cut through continental shelf)
Sediment
Continental shelf
Continental slope
Continental rise
Oceanic ridge
Continental
crust (granitic)
Oceanic
crust (basaltic)
Asthenosphere

19. Atlantic = Passive Margin
An active margin
Narrow continental shelf
Peru–Chile Trench
A passive margin
Plate boundary
Andes Mountains
South America
Broad
continental shelf
Pacific Ocean
South American Plate
Deep basin
Atlantic Ocean
Nazca Plate
Plate movement
African Plate
Subduction zone (deep and shallow earthquakes)
Mid-Atlantic Ridge (spreading centers, shallow earthquakes)
Atlantic = Passive Margin
little/no geologic activity
Pacific = Active Margin
geologic activity

20. passive margin NO plate boundary at edge of continent
• shelf and slope
• continental rise
(less steep than slope)
• abyssal plain
(smooth, deep seafloor)

21. Continental shelf
Continental shelf: perluasan dari continent dan berhubungan dengan dataran pantai,
Kemiringan 0,1derajat
Lebar beberapa km – 50km, kedalaman 100 – 200 m
Umumnya Sedimen terakumulasi pada daerah ini  ke daerah C. Slope by: Turbidity current
Sedimen berasal dari continent Terrigeneous sediemet
Ditutupi oleh sedimen muda

22. most material comes from erosion of continent

24. Continental slope
Kemiringan bertambah yg menghubungkan the Continental shelf to abyssal plan.
Kemiringan slope 4 – 5 derajat
Kedalaman terus bertambah star m to – m

25. Continental rise
Kemiringan semakin berkurang,  0,5 derajat menghubungkan dasar laut dg continental shelf.
Masih dianggap bagian dari continental.
Berakhir pd abisal plan pd kedalaman kira 5 km
Berada di atas oseanik crust

26. Abyssal plains
Abyssal plains daerah datar yang terdapat di deep ocean basin floor.
Kenampakan plg datar di bumi dengan slope < 0,01 derajat
Umumnya terletak antara kaki continental rise dan a mid-oceanic ridge.
Kedalaman 4,000 – 6,000 m

27. Abyssal plains and abyssal hills cover most of Earth’s surface.
Abyssal Plains: Deep, flat areas that are composed mostly of sediment. The Atlantic Ocean has the most substantial.
Abyssal plains and abyssal hills cover most of Earth’s surface.
Abyssal plains
40% of the ocean floor
common in the Atlantic
rare in the Pacific
covered by sediment
Abyssal hills
small sediment-covered extinct volcanos or rock

28. Abyssal hills Hills (Bukit2) along the ocean floor.
Tinggi dan diameter bervariasi
Kebanyakan lebih besar dibanding bukit2 di darat.
meters high

29. Seamounts are volcanic projections from the ocean floor that do not rise above sea level. Flat-topped seamounts eroded by wave action are called guyots
Abyssal hills are flat areas of sediment-covered ocean floor found between the continental margins and oceanic ridges. Abyssal hills are small, extinct volcanoes or rock intrusions near the oceanic ridges.

30. Submarine Canyon
Submarine canyons - V-shaped valleys that run across continental shelves and down continental slopes
Deliver continental sediments to abyssal fans on deep sea floor, sometimes by turbidity currents

31. Submarine Canyons
Makes no sense without caption in book

32. Submarine Canyons Form at the Junction between
Continental Shelf and Continental Slope
These are features of some continental margins. They cut into the continental shelf and slope, often terminating on the deep-sea floor in a fan-shaped wedge of sediment.

33. Oceanic Trenches Oceanic trench-> daerah sempit,
Palung dalam, parallel thp sisi/tepi continent atau an island arc
Bagian yang paling dalam dari lautan

34. Mid-Oceanic Ridges
Mid-oceanic ridge - giant undersea mountain range extending around the world like the seams on a baseball
Made mostly of young basalt flows
More than 80,000 km long, 1,500-2,500 km wide, and rises 2-3 km above ocean floor
A rift valley, 1-2 km deep, runs down the crest of the ridge
Shallow focus earthquakes common
Extremely high heat flow
Often marked by line of hot springs, supporting unique biological communities
Offset along transform fracture zones

35. Mid-Ocean ridge
A mid-ocean ridge is an underwater mountain range, typically having a valley known as a rift running along its spine (punggung), formed by plate tectonics. It is usually an oceanic spreading center,which is responsible for seafloor spreading.

36. Coral Reefs
Coral (symbiotic coral + alga) are filter feeders, (at present) only live in fairly warm, clear, agitated waters.
Coral reefs are due to accumulation of the calcareous remains of corals and algae, along with minor contributions from other organisms, like sponges and shellfish.
Reefs come in three main types. First two are found in the geologic record, as well as live. Atolls are not found in the geologic record.
Fringe reefs occur along the margins of land. Only conditions needed by coral are necessary for fringe reefs to form. If sea-level is constant, they propagate seaward, leading to barrier reefs.
Barrier reefs occur offshore from land at the surf zone. As a fringe reef grows, the water above it becomes less agitated, a condition necessary for coral. Coral keeps growing in the surf zone, so the live part of a reef can be separated from the land. Fragmented bits of reef fill in the lagoon (quiet water area behind the reef). (Why would this be different for atolls?)
Atolls occur in deep water, and are usually circular rims of reef around a central lagoon. They form as fringe or barrier reefs around an island. The central lagoon is due to karst dissolution of the central part of an originally flat island when sea level was lower during the last glaciation. (We know this because a) we don't find ancient atolls and b) when we drilled a lot into Bikini Atoll, the lower part looked like a perfectly normal fringe reef, and the upper bit looked like it had been karsted, and partially filled in)

37. other sea floor features
seamount
conical mountain that
rises > 1,000 m
above sea floor;
basaltic volcanoes;
chains of seamounts
occur
(aseismic ridges)
(Emperor seamounts)
guyot
flat-topped seamount;
erosion from waves;
reefs common around
them

38. Sea Mount
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface (sea level), and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly.

39. Volcanic seamounts and guyots project above the seabed
>1 km in height
important fishing areas
seamount
about 30,000
about 10,000 in the Pacific
Emperor Seamounts

40. Guyot
A guyot also known as a tablemount, is a flat-topped seamount. Their flatness is due to erosion by waves, winds, and atmospheric processes.

41. Guyot: flat-topped seamount that once reached the surface

42. Trench
The oceanic trenches are hemispheric-scale (one hemisphere to another) long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor.

43. Mariana Trench
Is the deepest part of the world's oceans, and the deepest location on the surface of the Earth's crust. It has a maximum depth of about 10,911meters, or 11 kilometers.

44. Atlantic

45. Dimana atoll tedapat?
Most of the world's atolls are in the Pacific Ocean and Indian Ocean
The Atlantic Ocean has no large groups of atolls other than eight atolls east of Nicaragua

46. Atoll
An atoll is an island of coral that encircles a lagoon partially or completely.

47. Terimakasih