Download 23.2 Features of Ocean Floor Notes (Student Copy)

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23.2 Ocean Ocean Basin Notes
Name ______________________________
19-2 Features of the Ocean Floor
2 major areas – continental ______________ & deep-ocean basin
Continental Margins – underwater part of continent, made of continental crust and a thick wedge of
There are _____ parts of a continental margin
1. Continental _____________
_____________ sloping part of content, extends to continental slope
Up to 1280 km (_______ mi) long!
Rarely more than 200 m (_________ft) deep
Most ocean ________________________ come from continental shelf because it’s
shallow enough to harvest there
2. Continental ____________
“Steep” edge of continent
Begins at shelf edge where water depth increases “rapidly”
20 km (______mi) wide, 3.6 km (________ mi) down, slope of _____
3. Continental ___________ - a gradual slope of sediment beginning at base of continental slope
Features of continental margins!
Submarine canyons – large underwater valleys cutting through continental shelf
Caused by rivers as flowing water erodes edge of continent
_____________ _____________ also create submarine canyons
Underwater landslides, dense currents of sediments
Caused by earthquakes or when lots of dense sediment builds up
The ____________ river created one off the coast of ________________!
___________ Fan – pile of sediment that forms where a submarine canyon meets the ocean floor
Two types of Continental Margin – active & passive
1. Active continental margin – located at ___________ __________________
Convergent boundary – denser oceanic plate _____________ beneath the continental plate.
________________ occur on the edge of the continents where this happens.
– Transform boundary – plates slide past one another, cause _______________
– Deep ocean _________________ can be found near active boundaries
2. Passive continental margins – not located at plate boundaries.
– No deep ocean trenches.
– Coastal ____________ are found along passive margins.
Deep-Ocean Basins
Abyssal _____________
Vast, flat areas of deep-ocean basin where ocean is more than 4 km (_____ mi) deep
Flattest places on Earth! 1,300 km (_____ mi) only change 3 m (_____ ft)
Covered with fine __________________ (caused it to be flat, as snow does)
Most carried from land by rivers, some falls from obove
Thickness depends on age, distance from continent, and if it’s bordered by trenches
The older it is, the ______________ the sediment
Abyssal _____________ - rolling hills in ocean (<1 km), often found near oceanic ridge
Laurentian Abyss – off east coast of Canada, about 6.0 km (_____ mi) deep
Long, narrow depressions that run parallel to continental ________________________
Form at the edge of ______________ zones (2 plates)
Earthquakes, volcanic mountain ranges, and volcanic ______ arcs form near trenches
Mariana Trench – deepest part of ocean, over 11 km (almost ______ mi) deep
In western Pacific Ocean, south of ________________
Deeper than Mt. _____________________
19.2 Ocean Basin Notes Continued
Name ______________________________
Mid-Ocean Ridges
Underwater mountain ranges that run along floors of oceans
Form chain over 50,000 km (________ mi) long!
Rarely rise above sea level (at _______________ & ______________ Islands they do!)
Form at _______________________boundary, where plates are moving _______________ (a
process called ____________________ spreading)
______________ valley in middle where new seafloor forms
Azores Islands
On Mid Ocean Ridge (formed via _______________ eruptions)
Have lava _____________, _______ springs, cook food in ________________
Hydrothermal Vents
Discovered in ______________
Water seeps into cracks in ocean floor, becomes _________________ & dissolves minerals,
shoots out of vents, minerals precipitate back out
1st ones were discovered near _________________ Islands
Black smoker chimney – “smoke” is superheated (350oC or _____oF) fluids filled with dark
_______________ particles
Scientists realized that hydrothermal vents were great furnaces where many of Earth’s
great _________ (metal) ___________ formed
Biggest chimney named _________________ was ______ ft wide & ______ stories tall
Sulfate in seawater is converted into hydrogen sulfide as seawater seeps into hot ocean crust
Bacteria & other microorganisms use _________________ _______________ (_____)
Entire ecosystems that don’t need _______________________ for energy! Instead they
live on __________________ energy!
Hundreds or thousands of species there!
Tubeworms, white ______________, pink fish, clams, octopus
Some of the critters disintegrate if you try to bring them to the ______________
Vents are only active a few _______. When vents stop, all organisms that can’t find new
vents die
Submerged volcanic mountains taller than 1 km (____ mi)
Form over _______ spots, can form volcanic _______________
___________________ is over a hot spot!
___________________ is the tallest mountain on Earth – 10.2 km high (____ mi)
___________________ is the highest mountain
______________ (aka Tablemounts)
Flat-topped underwater mountains that form when
1. Volcanic island sinks
2. __________________ erode island, making it flat
3. Flat topped island sinks below sea level…then it’s a ________________!
Coral Atolls
Coral - marine invertebrates typically living in compact colonies of many identical individual "polyps".
They’re ___________________! They eat _____________________ that live inside their bodies.
Coral Atoll - ring-shaped coral island
Forms when:
1. coral grows in the shallow area around ______________island
2. volcanic island eventually sinks below sea level, leaving a ring of ______________
Bikini Atoll
Used as a ________________ ___________ test site;
Barrier reefs
Coral reef – limestone formation of corals & coral ______________
______________ reef – coral reef that forms around island or short distance from shore
Creates “barrier” to ships trying to land…like Magellan!
Great Barrier Reef
Off northwestern shore of ____________________________
One of the 7 wonders of the natural world
Longer than the Great Wall of China; only living thing visible from ____________!
Blue Holes
Sinkholes were created by weathering ______________ during last ______________________
– Water dissolved deep holes in rocks (often in areas of karst topography; in limestone)
Ice melted, sea level _________, & sink holes filled with water, becoming blue holes
The Great Blue Hole
– Discovered by ____________________________, near Beliz, & popular for ________ diving
Not much oxygen, so critters don’t liver ther much
Deepest is in Mexico, 335 m (___________ ft) deep