Definitions

Question 1

oceans

Answer 1

critical to the habitability of the planet. govern weather, climate change, food production (on continents and ocean), they are dangerous to work in and extreme events occur there that impact society (e.g. hurricanes and typhoons). also tsunamis and large earthquakes.

Question 2

why oceans are changing

Answer 2

due to societal impacts such as over-fishing, climate change, etc.

Question 3

ocean is influenced/controlled

Answer 3

by numerous complex, dynamic, and interlinked processes. to learn to mange the oceans, we must understand the processes which may teach us how to mitigate the impact of damaging events (drought, storms, tsunamis, etc.)

Question 4

volcanoes

Answer 4

70% of the volcanism on the plant occurs beneath the ocean surfaces.

Question 5

Haiwaii and Iceland

Answer 5

volcanoes that are long-lived and large enough that they out crop above the oceans surface.

Question 6

mid ocean ridges

Answer 6

central to crust formation and life - 60,000 km mountain chain.

Question 7

submarine volcanoes (why we study them)

Answer 7

100,000’s of underwater volcanoes (seamounts). only 2-3 underwater eruptions ever witnessed. source of important metals (e.g. mercury, gold). drive hydrothermal flow, host amazing life forms. can be hazardous.

Question 8

1st reason volcanoes explode

Answer 8

magma chambers become over pressurized i.e. magma + volatiles continue to migrate into the chambers and eventually the overlying rocks are not strong enough to hold the pressure from the melt - remember seafloor spreading centers are under extension, with each tectonic plate pulling away.

Question 9

2nd reason volcanoes explode

Answer 9

the melts host significant carbon dioxide as a gas phase. ~85% of earth’s magmatic budge is focused at mid-ocean ridges. most of the submarine volcanism occurs at mid-ocean ridge spreading centers where the plates spread apart at rates similar to the rate that your finger nail grows.

Question 10

convection

Answer 10

major planetary process that drives things such as overturn of materials in the core of the earth and hydrothermal flow. one way it occurs is when cold materials are heated from below and the fluids begin to overturn because of the rise of heated fluids.

Question 11

convection process for submarine volcanoes

Answer 11

At mid-ocean ridges, cold seawater migrates down into the crust along cracks. It is heated by magma chambers (holding tanks for 1200°C basaltic melt) or hot rock from crystallized (fossilized) chambers at depths of ~ 1 to 8 km beneath the seafloor. With heating, the fluids become less dense and buoyant such that they rise to the surface..convection/overturn of the fluids occurs as cold, dense seawater migrates down along fractures in the seafloor and the super heated (>400°C) hydrothermal fluids rise to the surface. Once convection cells are established, the cold seawater migrates downward to replace the upwelling fluids that exit the seafloor.

Question 12

black smokers

Answer 12

result in part from the convection process. As the seawater-derived fluids heat up, they become acidic (pH 1-5), interact with the basalts and leach out metals, and they become enriched in CO2 and other gases from the magma. When these hot, acidic fluids hit the near-freezing seawater at the seafloor, fine-grained metals (such as pyrite - also called fools gold) precipitate out forming black plumes

Question 13

important characteristics of hyrdothermal vents: black smokers

Answer 13

found on all spreading centers; fueled by cooling volcanoes; pressures 200-400X atmospheric; boiling is common with temperatures >400 C; fluids enriched in CO2, CH4, H2S, metals, and acidic; support dense and diverse biological communities; and most extreme environment on earth, supports life at >121 C.

Question 14

snow blowers

Answer 14

microbial blooms appear to be associated with eruptions. The microbes live in the absence of sunlight and oxygen and are supported by gases (carbon dioxide, methane, hydrogen sulfide, hydrogen) given off from the underwater volcanoes. They represent some of the most extreme life on the planet -i.e. they can live at temperatures >200°F, thrive on toxic gases, and some utilize metals such as arsenic, mercury, and cobalt. It is thought that the microbial blooms result from increased degassing of carbon dioxide out of the volcano and increased fluid flow in the crust just prior to, during and following an eruptions or intrusion of melt into the seafloor.

Question 15

snow blower microbes

Answer 15

Investigation of these microbes is important because they provide hints to life forms that thrive beneath the seafloor, and because the vents may be important sources for organisms found throughout the oceans. Some organisms host the most genetically ancient DNA known, providing hints to the origin of life that is thought to have started in seafloor hot springs. important to society - medicines from the sea, industrial applications. biomass of seafloor may rival that on the continents.

Question 16

melt lava sources

Answer 16

Magma at mid-ocean ridges (which is eventually held in magma chambers at depths of ~ 1-8 km beneath the seafloor) is formed when upwelling mantle material rises (decompresses) beneath the spreading centers. The mantle material is plastic- like but at depths of ~ 75 km beneath the ridges, decompression results in melting of this material. Peridotite is the rock name for mantle material.We do not know the exact nature of the channel network that rises up through the mantle to the magma chambers, but presumably, small channels grow into larger ones at more shallow depths that allow magma/melt to accumulate in the subseafloor.

Question 17

melt within magma chambers

Answer 17

1200°C. The rocks that cap the chambers near the melt- completely crystalline interface are at ~ 70-750°C. When the pressure in the magma chamber overcomes the strength of the overlying rock (remember mid-ocean ridges are an extensional environment), the crystalline cap rock fractures and a dike (pipe-like body) of melt (~ 1 m in width, 1to >5 km in height is intruded into the crust. If there is enough magma + volatile pressure, the melt reaches the seafloor as a lava flow (1200°C). As the hot lava hits the cold seawater, the surface rapidly quenches such that the surface of new lava flows is glass.

Question 18

sheet flows

Answer 18

eruptions of lava on the seafloor at the beginning of the eruption; nearly flat. These may form as pools of lava that form lava lake crystallize, or as sheets of fast moving lava that migrate across the seafloor.

Question 19

pillow flows (pillow basalts)

Answer 19

opposite end of sheet flows; form bulbous forms with striations on the surface. these are slow moving flows that typically occur near the end of an eruption. In between these two morphologies are lobate flows that have lower relief than pillow basalts.

Question 20

lithosphere

Answer 20

overlies the mantle, is rigid, and deforms by facturing. also called the ocean crust. beneath mid ocean ridges this is ~8-11 km thick.

Question 21

mantle

Answer 21

very hot, plastic like material. ~200 km in thickness. deforms ductilly.

Question 22

peridotite

Answer 22

dominant rock of the upper part of the Earth’s mantle. provide samples of the Earth’s mantle brought up from depths ranging from about 30 km to 200 km or more.

Question 23

how melt gets to sea floor

Answer 23

melts rise up through the mantle and through the lithosphere (crust). with lessening pressure (decompression), the mantle begins to melt. melting beings at ~75 km depth beneath the spreading center. // melts rise from within the mantle where convection is important. heated fluid moves away from the heat source, become less dense and rises.