LAB3 HW
docx
keyboard_arrow_up
School
El Camino Community College District *
*We aren’t endorsed by this school
Course
10
Subject
Geography
Date
Feb 20, 2024
Type
docx
Pages
5
Uploaded by ChancellorScienceNightingale40
MAJOR OCEAN-FLOOR FEATURES LAB
Objectives: for you to recognize important ocean-floor features, and where appropriate, to relate them to plate tectonics theory. You need to have Google Earth Pro on your desktop or device (see resources below) Terms
passive continental margin
- continental crust is welded to oceanic crust; not a plate boundary. Earthquakes are rare, and volcanic activity is nonexistent. Typically, a passive margin is greater that 200 miles away from the nearest plate boundary. Continental shelves along passive margins tend to be broad, often from 50 to 300 miles across.
active continental margin - where a plate boundary is near a continent’s shoreline; typically, less than 200 miles from edge
of continent. Volcanism is common, especially where subduction occurs just off shore, and earthquake activity is prevalent, promoting mass wasting of continental shelf edges, keeping shelves from growing as wide as their passive margin equivalents. Most active-margin shelves are less than 50 miles across.
submarine fan
- large wedge of sediment formed where currents flowing from a submarine canyon deposit sediment at the
base of a continental slope. Sediment which composes a submarine fan is derived from the weathering and erosion of inland mountains. Streams/rivers then deliver the sediment into the ocean where it is eventually carried down into deeper
water. Major rivers (Nile, Ganges, Mississippi) are associated with the largest submarine fans. Continental Shelves
1)
In your own words, what is a continental shelf?
A continental shelf is a slightly sloping and shallow area of the ocean floor that extends outwards from the edge of
a continent. 2)
On your copy of the Physiographic Chart of the Sea Floor (below), use a green pencil to indicate the positions of shelves at all passive continental margins, and a blue pencil to indicate the positions of shelves along the active continental margins. (if you do not have a printer, color it using on Microsoft Words, PowerPoint, or edit it using your cellphone (let me know if you struggle with this part)
https://www.deepseanews.com/2015/07/its-time-to-geek-out-over-a-new-global-bathymetric-data-set/
3) Use Google Earth (GE) to measure the widths of the following shelves, perpendicular to the shoreline out to the shelf edge. Follow the links (or google resources) to learn how to measure distances using Google Earth (in kilometers)
http://earth.google.com/intl/ar/userguide/v4/index.htm
https://www.businessinsider.com/how-to-measure-distance-on-google-earth
https://support.google.com/earth/answer/9010337?co=GENIE.Platform%3DAndroid&hl=en
https://www.youtube.com/watch?v=ysMo6cZQtHk
For each, indicate if it is at an active or a passive margin based on the distance from shoreline to the nearest plate boundary. Indian Ocean
a) shelf at southern tip of South Africa: 244 kilometers 152 miles active/passive PASSIVE b) western shelf of Madagascar: 28.6 kilometers 17.8miles active/passive PASSIVE c) shelf west of Bombay: 4.74kilometers 2.95 miles active/passive PASSIVE
d) shelf south of Java Island: 0.92 kilometers 0.57miles active/passive ACTIVE Pacific Ocean
a) shelf west of Lima: 16.5 kilometers 10.2 miles active/passive ACTIVE b) shelf west of Los Angeles: 2.49 kilometers 1.55 miles active/passive ACTIVE c) shelf east of Kamchatka Peninsula: 37.2 kilometers 23.1 miles active/passive ACTIVE d) shelf between Australia and Great Barrier Reef: 151 kilometers 94 miles active/passive PASSIVE Atlantic Ocean
a) shelf east of Valdes Peninsula: 1.3 kilometers 0.81 miles active/passive PASSIVE b) shelf east of New York: 193 kilometers 120 miles active/passive PASSIVE c) shelf west of Lisbon: 122 kilometers 75.8 miles active/passive ACTIVE d) shelf north of Puerto Rico: 39.9 kilometers 24.8 miles active/passive ACTIVE 4) Calculate the average width of passive continental margin shelves for all of the ocean, from the above calculations. 103.7 kilometers 47.92666 miles
5) Calculate the average width of active continental margin shelves for all of the ocean, from the above calculations. 36.5 kilometers 22.67 miles
6) Provide a hypothesis to explain why the average widths of active and passive shelves are so different (think of plate tectonics).
Active continental margins have narrow, relatively steep shelves while passive continental margins have wide , shallow shelves and also gentle slopes.
Continental Rises
1) In your own words, what is a continental rise? A continental rise is the gently sloping area between the bottom of the continental slope and the deep ocean floor. 2) On your Physiographic Chart of the Sea Floor (see the map above), use a red pencil to indicate the locations of major submarine fans (must have four). To find them, think of the largest rives in the world and see if they have submarine fans.
Label each fan according to the names on the World Maps above. 1) Bengal fan
2) Indus fan
3) Amazon fan
4) Mississippi fan
5) Nile fan
6) Congo fan
7) la Jolla.
8) Horizon fan.
9) Hudson submarine fan.
3) What is the source of the sediment comprising the Indus and Ganges fans (where does the sediment come from; think of a geographic location)? The Indus River watershed, From the rivers emptying in the Indian Ocean.
How does that sediment reach the Indian Ocean? The Indus Fan gets sediment from the watershed of the Indus River.
The Ganges Fan collects silt from the Ganges and Brahmaputra river basins.
The Indian Ocean possesses the most suspended sediments of the three oceans, with over half originating from the Indian subcontinent alone. Terrigenous sediments are typically found on continental shelves, slopes, and rises, where they mix to produce abyssal plains.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
4) Calculate the approximate areal size of the Ganges Fan (area = length x width)
A= 1900 mi x 890 mi
A= 1691000 miles 2705600 kilometers 1691000 miles
5) How is the Amazon River related to the Amazon Fan?
The Amazon River carries sediment and other materials from the Andes Mountains to the Atlantic Ocean, where they are dumped and form the Amazon Fan. The fan is a large underwater delta at the mouth of the river. It is made up of gravel, sand, and mud that were carried by the river. Over time,
the sediment that falls into the ocean builds up into the fan-shaped structure. So, the Amazon River is where the Amazon Fan gets its dirt.
Abyssal Plains
1) In your own words, what is an abyssal plain?
Abyssal plains are the biggest ecosystem on Earth, occupying 70% of the ocean bottom at depths of over 10,000 feet. These deep, gloomy ecosystems are less productive than those around the continental shelf because sunlight cannot reach the sea bottom. Abyssal plains are featureless, very flat plains found on the bottom of the deep ocean. The abyssal plains are perhaps the flattest places on the planet. Abyssal plains occupy a substantial area of the bottom between the depth of 3000m to 6000m. Previously thought to be featureless plains, modern technology has revealed that they are just as uneven as the continental plain or surface.
3)
Why are abyssal plains so flat and featureless?
Abyssal plains are flat and featureless because they are located on the ocean floor at depths of about 3,000 to 6,000 meters. At these depths, the water pressure is extremely high, which prevents the formation of any significant topographical features. Additionally, the sediment that accumulates on the abyssal plains is mostly fine-grained and does not have the ability to form distinct landforms. Furthermore, the movement of the ocean currents is relatively slow at these depths, which also helps to keep the sediment in place and prevent erosion. All of these factors combine to create the flat and featureless appearance of the abyssal plains.
3) Calculate the approximate surface area of the largest abyssal plain on the Atlantic Ocean floor.
900,000 kilometers 559234.073 miles
Hawaiian-Emperor chain of islands and seamounts
1) Locate this chain of islands/seamounts on your Pacific Ocean World Map. The Big Island, Hawaii, is volcanically active today. The cluster of seamounts at longitude 174 degrees east and latitude 35 degrees north are also volcanic in origin, but are approximately 40 million years old. At the north end of the Emperor Seamount Chain of volcanoes, the Detroit Tablemount is roughly 65 million years old. All the volcanoes mentioned above were formed at the same hotspot,
now beneath the Big Island.
a) What was the rate and direction of motion of the Pacific Plate from 65 to 40 million years ago?
rate = distance/ 15,000,000 rate = 7.6 cm/year direction = NORTHWEST
b) What was the rate and direction of motion of the Pacific Plate from 40 million years ago to the present?
rate = 8.5 cm/year direction = WEST
2) Speculate as to why the rate and direction of Pacific Plate movement changed 40 million years ago. (Hint: What causes the plates to move?)-can be found from the last lab video. Around 40 million years ago, the Indian Plate and Eurasian Plate Collision had a significant impact on the rate and direction of Pacific Plate movement. The force of the collision between these two plates was so great that it shifted the rate and direction of the Pacific plate's movement from a northern to a northwesterly direction, and the rate was changed to between 5 and 10 centimeters per year. This further demonstrates the interconnectedness of all tectonic plates, which means that the movement of one or more tectonic plates affects the movement of other tectonic plates as well.