mapping the ocean floor. essential questions n what are some of the features found on the ocean...
TRANSCRIPT
Mapping the Ocean FloorMapping the Ocean Floor
Essential QuestionsEssential Questions
What are some of the features What are some of the features found on the ocean floor?found on the ocean floor?
What technology is used to map What technology is used to map the ocean floor?the ocean floor?
What are some of the features What are some of the features found on the ocean floor?found on the ocean floor?
Continental ShelfContinental Shelf
A flat, wide margin is found around A flat, wide margin is found around every continent every continent
The average width of a continental The average width of a continental shelf is 70 kilometers shelf is 70 kilometers
Slopes at an angle of 0.1°, or 1.7 Slopes at an angle of 0.1°, or 1.7 meters per kilometer meters per kilometer
Continental SlopeContinental Slope
The continental slope is about 16 The continental slope is about 16 kilometers wide, on average, and kilometers wide, on average, and descends to a depth of about 2.4 descends to a depth of about 2.4 kilometers kilometers
The slope of the ocean floor The slope of the ocean floor becomes much steeper, typically a becomes much steeper, typically a 4° slope, or 70 meters per 4° slope, or 70 meters per kilometer. kilometer.
is grooved by submarine canyons is grooved by submarine canyons and gullies. and gullies.
Continental RiseContinental Rise
The slope moderates to a mere The slope moderates to a mere degree or two from horizontal degree or two from horizontal which is called the continental rise which is called the continental rise
Submarine CanyonSubmarine Canyon
is a steep-sided valley on the sea is a steep-sided valley on the sea floor of the continental slope floor of the continental slope
cutting the continental slopes have cutting the continental slopes have been found at depths greater than been found at depths greater than 2 km below sea level. 2 km below sea level.
Oceanic TrenchOceanic Trench
Is where an oceanic crust plate begins to Is where an oceanic crust plate begins to descend beneath another oceanic crust descend beneath another oceanic crust plate plate
Oceanic trenches typically extend 3 to Oceanic trenches typically extend 3 to 4 km below the level of the surrounding 4 km below the level of the surrounding oceanic floor. oceanic floor.
Trenches are generally parallel to a Trenches are generally parallel to a volcanic island arc, and about 200 km volcanic island arc, and about 200 km from a volcanic arc. from a volcanic arc.
The greatest ocean depth to be sounded The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana is in the Challenger Deep of the Mariana Trench, at a depth of 10,911 m below sea Trench, at a depth of 10,911 m below sea level. level.
Abyssal Plain Abyssal Plain
The abyssal plain, which is the The abyssal plain, which is the deepest, most level part of the deepest, most level part of the ocean, is found where the ocean, is found where the continental rise ends, at a depth of continental rise ends, at a depth of about 4 kilometers. about 4 kilometers.
The abyssal plain is dotted with The abyssal plain is dotted with thousands of small, extinct thousands of small, extinct volcanoes called abyssal hills. volcanoes called abyssal hills.
Mid-Ocean Ridge Mid-Ocean Ridge
a long, undersea mountain chain a long, undersea mountain chain that usually extends down the that usually extends down the middle of the oceanmiddle of the ocean
The Mid-Atlantic Ridge, for The Mid-Atlantic Ridge, for example, snakes down the middle example, snakes down the middle of the Atlantic most of the way of the Atlantic most of the way from the North Pole to Antarctica. from the North Pole to Antarctica.
Rift Valley Rift Valley
Along the center of the mid-ocean ridge is Along the center of the mid-ocean ridge is the rift valley, a deep V-shaped notch. the rift valley, a deep V-shaped notch.
From this valley, new oceanic crust is From this valley, new oceanic crust is constantly being extruded from Earth's constantly being extruded from Earth's mantlemantle by processes not yet fully by processes not yet fully understood. understood.
In the case of the Mid-Atlantic rift valley, In the case of the Mid-Atlantic rift valley, one sheet flows east and the other west, one sheet flows east and the other west, each moving at about half an inch per year.each moving at about half an inch per year.
This causes sea floor spreading.This causes sea floor spreading.
GuyotGuyot
is an isolated underwater volcanic is an isolated underwater volcanic mountain, with a flat top over 200 mountain, with a flat top over 200 meters (660 feet) below the meters (660 feet) below the surface of the sea. surface of the sea.
the diameters of these flat the diameters of these flat summits can exceed 10 km. summits can exceed 10 km.
SeamountSeamount
is a mountain rising from the is a mountain rising from the ocean seafloor that does not reach ocean seafloor that does not reach to the water's surface, and thus is to the water's surface, and thus is not an island. not an island.
these are typically formed from these are typically formed from extinct volcanoes, that rise extinct volcanoes, that rise abruptly and are usually found abruptly and are usually found rising from a seafloor of 1,000–rising from a seafloor of 1,000–4,000 metres depth 4,000 metres depth
Hydrothermal ventHydrothermal vent
is a fissure in a planet's surface is a fissure in a planet's surface from which geothermally heated from which geothermally heated water issues water issues
are commonly found near are commonly found near volcanically active places, areas volcanically active places, areas where tectonic plates are moving where tectonic plates are moving apart, ocean basins, and hotspots apart, ocean basins, and hotspots
Interesting factsInteresting facts
Mauna Kea, Hawaii, rises 33,474 feet Mauna Kea, Hawaii, rises 33,474 feet from its base on the ocean floor; only from its base on the ocean floor; only 13,680 feet are above sea level13,680 feet are above sea level
The ocean ridges form a great mountain The ocean ridges form a great mountain range, almost 64,000 km long, that range, almost 64,000 km long, that weaves its way through all the major weaves its way through all the major oceans. It is the largest single feature oceans. It is the largest single feature on Earthon Earth
Deepest point - Deepest point - 36,198 feet in the 36,198 feet in the Mariana Trench in the western Pacific. Mariana Trench in the western Pacific.
What technology is used What technology is used to map the ocean floor?to map the ocean floor?
HistoricallyHistorically
For hundreds of years, the only way to For hundreds of years, the only way to measure ocean depth was the sounding measure ocean depth was the sounding line, a weighted rope or wire that was line, a weighted rope or wire that was lowered overboard until it touched the lowered overboard until it touched the ocean floor. ocean floor.
Not only was this method time-consuming, Not only was this method time-consuming, it was inaccurate; ship drift or water it was inaccurate; ship drift or water currents could drag the line off at an angle, currents could drag the line off at an angle, which would exaggerate the depth reading. which would exaggerate the depth reading.
It was also difficult to tell when the It was also difficult to tell when the sounding line had actually touched bottomsounding line had actually touched bottom
Present DayPresent Day
SONARSONAR– acronym for acronym for SOSOund und NNavigation avigation AAnd nd
RRanging anging is a technique that uses sound is a technique that uses sound
propagationpropagation– SONAR waves are sent from a ship and SONAR waves are sent from a ship and
the time for the waves to return is the time for the waves to return is measuredmeasured
– the farther the distance the longer the the farther the distance the longer the time, the shorter the distance the time, the shorter the distance the smaller the timesmaller the time
Sea 3-D: Charting the Sea 3-D: Charting the Ocean Floor - KQED Ocean Floor - KQED QUESTQUEST
http://www.youtube.com/watch?v=http://www.youtube.com/watch?v=1h4vaERMNbs1h4vaERMNbs
5:595:59
Oceanfloor LegacyOceanfloor Legacy
http://video.google.com/videoplay?http://video.google.com/videoplay?docid=862857452234843312#docid=862857452234843312#
28:28:
America's New Frontier America's New Frontier
http://video.google.com/videoplay?http://video.google.com/videoplay?docid=-7837963317498620058#docid=-7837963317498620058#
27:3027:30