Cot curve, melting temperature, unique and repetitive DNA
Hotspot,Margins
1. Sea Floor
• Geologically distinct from the
continents
• Perpetual cycle of birth and
destruction that shapes the oceans
and controls the geology and
geological history of the continents
2. Sea Floor Processes
• Occur slowly (hundreds of millions of
years)
• Solid rocks flow like liquid
• Entire continents move over the face
of the earth
3. Geology is Important to the Marine
Biologist
• Habitat – natural environment that an
organism lives
• Habitats are shaped by geological
processes
5. The Water Planet
• Presence of water makes earth
unique
• Oceans cover 71% of the globe
• Regulate our atmosphere and
climate
• Life would be impossible without
water
6. The Geography of the Ocean Basins
• 2/3 of land area is in Northern
Hemisphere
• 61% of N. Hemisphere is ocean
• 80% of Southern hemisphere is
ocean
15. The Theory of Plate Tectonics
• Wegner could not explain how the
continents could move so his theory was
not well accepted
• 1950’s and 1960’s evidence was put
together that proved that continents did
drift
• The process involves the entire surface of
our planet – plate tectonics
16. Discovery of the Mid-Ocean Ridge
• After WW II sonar allowed the first
detailed surveys of large areas of the sea
floor
• Lead to the discovery of the Mid-ocean
Ridge
• A continuous chain of submarine volcanic
mountains that encircles the globe like the
seams of a baseball
22. Hot spot
• Found in about 45 places around the
world
• Hot, molten rock or magma well up from
deep within the mantle
• This magma forces its way up through the
lithosphere
• Erupts in volcanic activity
• May be near or far from Tectonics plate
boundaries
23. Hot Spot Examples
• Geysers and bubbling mud pools at Yellowstone
result from volcanic activity
• Seamounts – volcanic underwater mountains
• Hawaiian islands were created from hot spots –
as the plate moved new islands formed
• Island chains in the south pacific
24. • Hot spots by mid-ocean ridges also form
islands – Ex. Iceland, Azores and the
Galapagos islands
28. Island Arc
• There are two ways in which a group of islands can
form.
• 1.) As a lithospheric slab is being subducted, the slab
melts when the edges reach a depth which is sufficiently
hot. Hot, re-melted material from the subducting slab
rises and leaks into the crust, forming a series
of volcanoes. These volcanoes can make a chain of
islands called an "island arc"..
29. Island Arc
• Examples of island arcs are the Japanese islands, the
Kuril Islands, and the Aleutian Islands of Alaska, shown
here.
• Island Arcs are formed on the opposing edge of a
subducted slab. For each case, there is an associated
subducting slab and a trench.
• 2.) The second way in which islands are formed is
via plumes or hot spots in the lithosphere. The Hawaiian
Islands are an example of this type of island formation.
In this case, there is no associated subducting slab
30.
31.
32. Sea Floor
• Divided into two main regions
• Continental margins – submerged edges
of the continents
• Deep-sea floor itself
33. Continental Margins
• Boundaries between continental crust and
oceanic crust
• Sediments from land accumulate here (can be
as thick as 10 km or 6 miles)
• Constitute about 28% of the oceanic area
• Shallow, gently sloping region (continental
shelf)
• Steeper area (continental slope)
• Gently sloping region (continental rise)
34.
35.
36. Continental Shelf
• Shallowest
• 8% of the oceans surface
• Biologically the richest part of the ocean (most
life and best fishing)
• Submarine canyons – remnants of rivers and
glaciers that once flowed across the continental
shelves
37. • Varies in width from less than 1 km (.6 mi)
to 750 km (470 mi)
• Shelf ends at the shelf break where the
slopes gets abruptly steeper
• Shelf break usually occurs at depths of
120 to 200 m (400 to 600 ft)
38. Continental Slope
• Closest thing to the exact edge of the
continent
• Begins at the shelf break and descends
downward to the deep sea floor
39. Continental Rise
• Deep sea fan – sediment moving down a
submarine canyon accumulated at the
canyon's base forms a deep sea fan (like a
river delta)
• Rise consists of a thick layer of sediment
piled up on the sea floor
42. Deep Sea Floor
• Depth of 3,000 - 5,000 m (10,000 to
16,500 ft.)
• Abyssal plain
• Rises at a very gentle slope towards
the ridge
43. • An active continental margin is found
on the leading edge of the continent
where it is crashing into an oceanic
plate. example is the west coast of
South America
• commonly the sites of tectonic
activity: earthquakes, volcanoes,
mountain building, and the formation
of new igneous rock
Types of continental Margins
44. Geological Features of the Abyssal Plain
• Submarine channels
• Low abyssal hills
• Plateaus, rises and other features
• Seamounts (submarine volcanoes)
• Guyots – flat topped seamounts
45.
46.
47. • Passive continental margins are
found along the remaining coastlines.
There is no collision or subduction,
tectonic activity is minimal and the
earth's weathering and erosional
processes are winning. This leads to
lots of low-relief (flat) land extending
both directions from the beach, long
river systems,
Types of continental Margins
48. • Accumulation of thick piles
of sedimentary debris on the
relatively wide continental shelves.
Again South America provides a
great example. The Amazon River,
whose source is in the Andes
Mountains (the active margin) drains
east across the interior of South
America to the coast,
Types of continental Margins
49. • where it enters the Atlantic Ocean
and deposits the tremendous volume
of sedimentary materials it eroded
from the continent.
Types of continental Margins
50. Trenches
• Plate descends into the
mantle
• Sea floor slopes steeply
downward
• Deepest parts of the
world ocean
• Mariana Trench –
Western Pacific – 11,022
m or (36,163 ft) deep
Editor's Notes
Hot spots not only mark the movement of plates, but they also play a part in the movement of plates. When a continent comes to rest, the dome that swells up over a hot spot is subject to fracturing and producing a three armed rift. These may initiate a zone of divergence and to guide the fracturing, although they are not necessarily the only cause. Typically, two arms of the rift open to form an ocean basin and the third arm fails and remains as a fissure in the continental landmass. By restoring the margins of the Atlantic Ocean to their Pangaea position, an abundance of three-armed rifts is revealed. The successful arms merged to form the mid ocean spreading zone and the unsuccessful ones remained as rifts extending into the continents.
