Chapter 3:Ocean bathymetry

fringing, barrier, atoll

what are 3 types of coral reefs ?

Continental Margin Features

continental shelf, shelf break, continental slope, continental rise

Satellite Altimetry

A satellite measures the variation of ocean surface elevation, which is caused by gravitational attraction and mimics the shape of the seafloor. extremely detailed

Why are the abyssal plains so flat?

Abyssal plains are created by the very slow suspension settling of fine sediments (mainly clay, dust, and ash) blown into the ocean by wind. When conditions are right, other types of sediments may accumulate on the deep ocean floor as well (such as hydrogenous manganese nodules or biogenous siliceous ooze.As the sediment settles on the ocean floor, it fills in any depressions and irregularities, creating a very flat seafloor over time.

active continental margin

Active continental margins are associated with a plate boundary that may be convergent active or transform active.

submarine canyon

Along the edge of the continental margins, submarine canyons cut into the continental shelf. Submarine canyons are created by turbidity currents, which are underwater landslides. They are water-saturated slurries of sediments that break off the continental shelf and fall down to the base of the continental slope due to gravity (just like landslides and rockfalls on land).

What are the average and maximum depths of the ocean?

Also notice that most of the ocean is between 3 and 6 kilometers deep (or 3,000-6,000 meters). The deepest spot on the ocean floor is the Mariana Trench with a depth of 11 kilometers (11,022 meters).

transform fault

Area where the earth's lithospheric plates move in opposite but parallel directions along a fracture (fault) in the lithosphere.

What does the hypsographic curve illustrate about Earth's surface?

Bathymetric (depth) data and topographic (elevation) data are used to create the Hypsographic Curve. The Hypsographic Curve illustrates the relationships between the height of land on Earth and the depth of the oceans.

What is bathymetry, and what are the four main methods that scientists use to study bathymetry?

Bathymetry is the study of the ocean floor, including ocean depth and the features on the ocean floor (similar to topographic maps on land that show mountains, valleys, hills, depressions, etc.). 4 main methods Multibeam Sonar; Side-scanning Sonar; Satellite Altimetry; and Seismic Profiling.

continetal margins

Continental margins are the edges of the continents where Earth's crust transitions from continental crust (mainly granite) to oceanic crust (basalt). Continental margins are classified as active or passive depending on the presence or absence, respectively, of a plate boundary at the edge of the continent.

What factors control the distribution and diversity of coral reefs?

Coral are temperature sensitive. They are restricted to warm, tropical waters (> 64o F all year, but must not exceed 86o F for long). For this reason, they are mainly limited to tropical waters between about 40o North and 40o South latitude. Notably, there is a greater distribution and diversity of corals on the west sides of the ocean basins. This is due to warm ocean currents and the presence of numerous tropical islands that favor speciation. Lower species diversities are seen in the Atlantic Ocean, largely owing to plate tectonics (

What are coral, and why are coral reefs important? Why are they threatened?

Coral reefs are composed of colonies of individual polyps. They are small benthic marine animals that feed with stinging tentacles similar to jellies. Coral secrete hard calcium carbonate structures (reefs) for protection.Corals live symbiotically with photosynthetic microscopic dinoflagellate algae called zooxanthellae that live within their tissues. It is the zooxanthellae that give the coral their color. Coral are important because their reefs provide shelter, food, and breeding grounds for numerous other species. Coral reef ecosystems are characterized by a diversity that surpasses even tropical rainforests. Coral cover <0.5% of the ocean's surface area, but are home to 25% of all marine species. They are important to humans because healthy reefs teeming with marine life support tourism, fisheries, and they prevent shoreline erosion.

deep-sea fans (submarine fans)

Deep-sea fans are created at the base of the continental slope by the turbidity currents. The deep-sea fans are composed of layers of graded bedding, and together, the fans create the continental rise.

Why are they threatened?

Human threats to corals include disease, pollution, bleaching, ocean acidification, destruction, overfishing (causes overabundance of algae that smother the reef), predation by species that are increasing because of humans, and sea level rise (reduces access to sunlight

multi-beam sonar

Multibeam sonar utilizes multiple frequencies of sound to generate detailed images of the ocean floor along a strip up to 60 km wide

What is graded bedding, and how does it form?

Once settled, the layers and layers of graded bedding are referred to as turbidite deposits because they were created by turbidity currents.

Passive Continental Margins

Passive continental margins are not associated with a plate boundary.

What are abyssal hills/sea knolls, seamounts, and tablemounts/guyots?How are they created on the seafloor?

Seamounts are created by underwater eruptions of (basaltic) lava. If only a small amount of lava bursts through the seafloor, an abyssal hill may form.Due to the motion of tectonic plates that will eventually carry a seamount off its source of magma, most seamounts on the ocean floor are extinct volcanoes that rise hundreds or thousands of feet from the seafloor. tablemounts (also called guyots), which form from eroded, flattened islands that have subsided back into the ocean, and volcanic islands.

Side Scanning Sonar

Side-scanning sonar also utilizes multiple frequencies of sound to generate detailed images of the ocean floor. Here, a side-scanning sonar instrument is towed behind a survey ship and can map a strip of ocean floor with a gap in data directly below the instrument. The ship goes back and forth across the ocean floor (in swaths) to map ocean depths and features

What organisms are at the base of the food chain in these communities?

The organisms at the base of the food chain here are chemosynthetic archaea.

seismic profiling

This method also uses multiple frequencies of sound, but it differs from the other methods in that it provides information about sub-surface materials and layers below the seafloor

Why are a majority of the world's trenches found in the Pacific Ocean basin?What is the Pacific Ring of Fire?

Trenches and volcanic island arcs also occur in the deep ocean when the tectonic setting is conducive to their formation. Recall from Module 3: The Wilson Cycle and Plate Motions Through Time that the Pacific Ocean is in the declining stage, because subduction occurs all around its edges, and the ocean basin is getting smaller over geologic time. This subduction creates the Pacific Ring of Fire, with active volcanic arcs (including island arcs and continental arcs) and deep-ocean trenches on the seafloor.

fracture zone

an area of irregular, seismically inactive topography, marking the position of once active transform faults

turbidity currents

an underwater current flowing swiftly downslope owing to the weight of sediment it carries.

Why does the mid-ocean ridge system have a zig-zag appearance?

bc the earth is cruved spread at different rates,we end up with offsets in the mid ocean ridge. youll have an axis of the ridge and then an offset

What are pillow lava/basalt and hydrothermal vents, and how do they form?

pillow basalt:When hot basaltic lava spills onto the ocean floor, it is exposed to cold sea water that quickly solidifies the outer layers of the lava, creating a crust. The hot inside is still hot and runny, so the lava continues to flow, sometimes breaking through the thin crust that was just created. This creates "pillow lavas" or "pillow basalts," that are smooth, rounded lobes of rock that resemble a stack of bed pillows (but they are not soft!). hydrothemreal vents:Hydrothermal vents are also associated with mid-ocean ridges. Hydrothermal vents are seafloor hot springs that are created when cold seawater seeps through cracks and fractures in the ocean crust and approaches an underground magma chamber. The water becomes superheated (since it can't boil and evaporate at such high pressures in the deep ocean). The superheated water dissolves minerals and ions in the rocks when it makes it way back up toward the ocean floor.

chemosynthetic bacteria

use the geothermal energy in hot springs or deep-sea vents to produce their food

How do hydrothermal vents and seeps support life?

vents :::::: The organisms at the base of the food chain in hydrothermal vent communities like this are not photosynthetic. They are archaea that live on the deep, dark ocean floor and have no access to sunlight. The organisms at the base of the food chain here are chemosynthetic archaea.Notice that chemosynthesis involves combining hydrogen sulfide, water, carbon dioxide, and oxygen to produce sugar and sulfuric acid. Photosynthesis involves combining sunlight, water, carbon dioxide, to produce sugar and oxygen. In hydrothermal vent communities, the hydrogen sulfide is emitted by the hydrothermal vents!Archaea thrive on sea floor chemicals, most notably hydrogen sulfide, and perform chemosynthesis. seeps::: These are areas where methane (natural gas) and hydrogen sulfide seep from cracks in rocks. These chemicals are used by bacteria to chemosynthetically produce food, thereby supporting a great diversity of marine life in deep ocean environments. The three main types of cold seeps are hypersaline, hydrocarbon, and subduction zone seeps.

How do seamounts, tablemounts, rift valleys, fracture zones and transform faults relate to mid-ocean ridges?

volcanic activity.Hydrothermal vents are associated with mid-ocean ridges at divergent plate boundaries and along oceanic-oceanic convergent boundaries as discussed above

What conditions do coral require?

warm water, strong sunlight,strong wave or current,lack of turbitity,salt water,hard substrate