Oceanography Quiz #3

DDT

A powerful insecticide that is also poisonous to humans and animals used in agriculture but too strong

Easter Island

An island in the eastern Pacific Ocean, part of Polynesia, known for its giant human head statues. famous for large stone statues left by earlier culture

passive margins and tectonic activity

Because passive margins do NOT involve a plate boundary, they are normally tectonically "quiet," with no volcanoes and few earthquakes

Galapagos Islands

Home to many unique species, such as the marine iguanas famous for their endemic species

ocean basins

Most of the seafloor is part of the ocean basin. ¡The deep ocean basin is where the ocean covers ocean crust.

seafloor two components

The Continental Margin The Ocean Basin

coral reefs

They can be associated with both continental margins and ocean basins around volcanic islands or seamounts.)

DDT and PBCs

biologically active classified as persistent organic pollutants (POPs) capable of causing cancer, birth defects, and other grave harm

features of ocean basin

include: Ocean Ridges Hydrothermal Vent Chimneys Trenches Seamounts Coral Reefs (which can also be on continental margins)

The Trieste

submarine that first explored the Challenger Deep 1960 descent

PCBs

synthetic chemicals containing chlorine that are used in the manufacture of plastics and other industrial products, become stored in the tissue of animals, and also persist in the environment liquid coolants and insulation industrial equipment used in wiring, paints, caulks, hydraulic oils, carbonless copy paper, and a hos of other products cause liver cancer and harmful genetic mutations in animals. affect animal reproduction

sewage sludge

the solid material that remains after treatment primary treatment= where solids are allowed to settle and dewater secondary treatment= exposed to bacteria-killing chlorine contains: human waste, oil, zinc, copper, lead, silver, mercury, pesticides, and other chemicals 500,000 metric tons into socal 8.8 million tons dumped into New York Bight

james cameron

visited titanic 33 times

corals

´Coral animals are typically very small. ´Many coral species have individuals that are the size of ants. ´So on a typical coral reef, millions of corals live in and build the calcium carbonate structure.

if corals are animals, why do they need sunlight?

´Most reef-building corals have a symbiotic relationship with photosynthetic algae called zooxanthellae. These algae live in the tissues of the coral. ´These algae create the vibrant colors of living corals.

Zooxanthellae in coral tentacles

´The algae photosynthesize and provide sugars (food) to the coral. ´The corals provide protection from predation and organic waste (as nutrients) to the corals. ´Additionally, the corals, like all animals in their phylum, have stinging tentacles and can catch their own food. ´There are coral species that live in deeper, colder water that rely entirely upon catching their own food to survive. They grow very slowly. Occasionally these species can build reefs, but they are less common and not as diverse as tropical reefs.

coral reefs

´The largest and most extensive coral reefs are tropical. The reef is composed of calcium carbonate (CaCO3). ´The Great Barrier Reef is the largest biological structure on the planet. It is about 2300 km long and up to 150 km wide. ´Tropical reef building corals require shallow clear water for maximum sunlight penetration. ´Tropical water, generally, is the clearest water because it has fewer micro-organisms in the water. ´Corals are animals with stinging tentacles, enabling them to catch prey. Their closest relatives are jellyfish and sea anemones.

active continental margin

•Active continental margins only occur in the Pacific Ocean. •At an active continental margin, a plate boundary, usually a subduction zone (trench), separates the continental crust from the adjacent ocean crust, so the continent and ocean crust are on different plates.

active margins and tectonic activity

•Because active margins DO involve a plate boundary, most commonly subduction, they experience more tectonic activity in terms of both volcanoes and more frequent and larger earthquakes.

continental margins

•Continental margins are that part of the continental crust that is covered by the ocean. •The continent does not end at the beach. It often extends hundreds of kilometers offshore from the beach.

turbidity current triggers

•Earthquakes, even minor ones that are not felt onshore. •Extreme wave turbulence in the water, such as from a passing hurricane or other extreme storm. •Rapid input of sediment from rivers after a flood event.

hydrothermal vent chimneys

•Hydrothermal vent chimneys primarily form on the flanks of ocean ridges, because they need a source of shallow magma for heat. •Chimneys form when seawater seeps into cracks in the seafloor and comes in close contact with the magma. •The magma heats the water to high temperatures. The hot water dissolves minerals from the surrounding rocks. •This mineral-laden hot water escapes through another seafloor crack. •Once the hot water comes into contact with the freezing ambient seawater, the dissolved minerals instantly precipitate (solidify) as tiny particles, visible as the "smoke." •The minerals settle to the bottom around the crack and slowly build up chimney structures, which can reach several meters in height. •These chimneys are often called "Black Smokers," although the smoke can be black, white, or gray. •This is a unique ecosystem in the ocean, with many endemic species. •It is the only deep sea ecosystem with abundant life, about 1000X the biomass of any other deep ocean ecosystem. •It is the only ecosystem on Earth which does not derive any energy from the sun.

iceland

•Iceland is one of the most volcanically active regions in the world, and the largest single island that is part of the ocean ridge system.

ocean ridges

•Ocean ridges are mature divergent boundaries and extend through all major ocean basins. •Placed end-to-end, ocean ridges stretch 65,000 kilometers (41,000 miles). •On average, the ridge rise 2 to 3 kilometers above the seafloor. (Earlier text in divergent boundaries said 1-2 km.)

two types of continental margins

•Passive continental margins •Active continental margins

passive continental margin

•Passive continental margins are the most common type of continental margin. •All continental margins bordering the Atlantic Ocean are passive. •All continental margins bordering the Indian Ocean are passive. •Some continental margins bordering the Pacific Ocean are passive. •At a passive continental margin, both the continent and the adjacent ocean crust are on the same plate with no plate boundary between them.

Europa (moon of Jupiter)

•Scientists believe that volcanic heat on the seafloor under Europa's oceans could create hydrothermal vent systems similar to those found on Earth. •This is the most likely possibility for life existing elsewhere in our solar system in the present.

seamounts

•Seamounts are submerged volcanic cones, that in most cases were once inactive islands that have sunk beneath the surface. •Occasionally they can be very young active volcanoes that have not yet reached the surface, such as Loihi off of the Big Island of Hawaii. •Seamounts can occur in a chain, or can be isolated individuals.

submarine canyons

•Submarine canyons are steep-sided canyons that cut deep into the continental slope on both passive and active margins.

mariana trench (deepest trench)

•The Mariana Trench, at 11 kilometers deep, is the deepest point on the Earth's surface. •Humans have visited the Mariana Trench on 4 occasions. •Two scientists ventured to the bottom of the trench in 1960. Their submersible cracked, but did not implode, luckily for them. Life was discovered in all 4 visits to the trench, but it was very sparse. •Lack of food is the main factor limiting life at the bottom of the trench, not pressure, cold temperatures, or lack of light. •In 2012, the film director James Cameron financed the building of his own submersible and visited the trench alone. •In 2019, an American investor, Victor Vescovo, also visited the bottom of the Mariana Trench (the deepest point, for the world record) twice, as well as the trenches in other ocean basins. The most notable thing that he discovered in the bottom of the trench was plastic garbage.

continental rise

•The continental rise is a layer of sediment that primarily extends off from the continental slope where the angle of descent lessens, and spreads across the adjacent ocean crust. There is no rise on a convergent active margin, as the sediment is carried directly into the subduction zone trench.

continental shelf

•The continental shelf is a relatively flat, very gently sloping region of the margin that extends seaward from the beach. •The average length of the shelf is 70 kilometers, but it varies from tens of meters to 1500 kilometers. •The average depth of the water at the end of the shelf (called the shelf break) is 135 meters. •Generally, the shelf is longer on a passive margin.

continental slope

•The continental slope begins at the shelf break at the end of the shelf and extends down to the deep seafloor. •It is a very gradual descent and vertically exaggerated in the previous diagram. •The slope is steeper on an active margin with a subduction zone.

Mid-Atlantic Ridge

•There are locations where the ridges are high enough to extend above sea level as islands. •Two of these locations in the Atlantic are Iceland and the Azores.

East Pacific Rise

•There are two regions of the East Pacific Rise that are above sea level as islands. •These are the Galapagos Islands and Easter Island. (Designated as Galapagos plate and Easter plate in this diagram.)

hypothesis for eastern island

•These islands are part of the ridge system, but have much more magma coming up in their location compared to the rest of the ridge. •One idea is that these locations are also over hot spots. •If they are over hot spots, these locations would have 2 sources of magma—the deep mesosphere would provide hot spot magma, and the shallow asthenosphere would provide the magma upwelling due to divergence.

Trenches

•Trenches are the deepest regions of the ocean. In the example here, the Peru-Chile Trench offshore from the west coast of South America is deeper below sea level than the tallest Andes mountains are above sea level.

turbidity currents

•Turbidity currents are fast-moving underwater avalanches that are a mix of seawater, rocks, sediment, and debris. •It is believed that over time, when they occur in the same location, they can cause enough erosion of sediment to create submarine canyons. •They deposit the sediment which makes up the continental rise. •A turbidity current was associated with the 1929 tsunami which occurred off of Newfoundland in the North Atlantic.