Ch 4. Distribution of Oceans and Continents Flashcards
Who proposed the Continental Drift Theory ?
Alfred Wegener in 1912
What is Continental Drift Theory ?
According to Wegener’s Continental Drift Hypothesis, all the landmasses were a solitary continental mass. This super continent was called Pangea and a super sea called Panthalassa encompased the landmass
When did Pangea split ?
200 million years ago
Pangea broke into ____ and ____
Laurasia and Gondwana
Which sea partitioned Laurasia and Gondwana ?
Tethys sea
What is Tillite ?
It is a sedimentary rock formed out of deposits of glaciers found in the Gondwana land system of sediments
What forces are responsible for the continental drift (according to Wegener) ?
- Pole fleeing force
- Tidal force
Thermal Convectional Current Hypothesis was given by ____ in the year ____
Arthur Holmes in the year 1928-1929
What is Convectional Current Hypothesis ?
The driving force of the mountain building is thermal convection currents which occur due to excess heat in the substratum where disintegration of radioactive elements generates heat regularly
What is a Continental Shelf ?
It is basically the streched margin of all the continents which is occupied by comparatively shallow gulfs and seas. It is the shallowest piece of ocean
What is the average width of an ocean shelf ?
80 km
The largest ocean shelf in the world is ?
Siberean shelf in the Arctic Ocean (480 km to 2,000 km (not imp.))
What is the depth of continental slope ?
180 - 3600 meters
What is Continental Rise ?
The base of the continental slope has some deposits of sediments. This belt of sediment is called Continental Rise
What is a deep sea plain / Abyssal plain ?
The plain area lying in between the foot of a continental rise and a mid-ocean ridge. Flattest and the most featureless area in the ocean
Depth of Abyssal plain is ?
3000 - 6000 meters
What are Oozes ?
The sediments which are developed from the remains of the living organisms are known as Oozes
How are Trenches or Oceanic Deeps formed ?
They are formed due to tectonic activities like ocean-ocean plates convergence or ocean-continent convergence
What is the deepest trench in the world ?
Mariana Trench off Guam Islands in the Pacific Ocean is the deepest trench with a depth of more than 11 km
What are Mid-Oceanic ridges ?
These are submerged mountain ranges, formed by plate tectonics. It is made of two chains of mountains separated by a large depression
What is a seamount ?
A mountain having pointed peak, mounting from the seafloor and which usually do not reach the surface of the ocean. They are generally 3000 - 4000 meter tall
Which is the largest Canyon on earth ?
Congo Canyon
What is a Guyout / Table mount ?
A flat-topped seamount
What is an Atoll ?
A ring shaped coral reef containing a coral rim which encompasses a lagoon completely or incompletely
Who gave the theory of Sea Floor Spreading ?
Harry Hess in 1962
What is Seafloor spreading ?
Seafloor spread is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.
In the Trenches where subduction occurs, the value of the gravitational constant ‘g’ is more. True or false ?
False
Who gave Plate Tectonic Theory ?
McKenzy and Parker in 1967
What is Plate Tectonic Theory ?
Theory that considers the Earth’s lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years .
Which tectonic plate is moving fast ?
East Pacific Rise in the region of South Pacific (around 3400 km west of Chile) has the fastest rate (more than 15cm per year)
Which tectonic plate is moving slower ?
Arctic Ridge has the slowest rate (less than 2.5 cm / year)
What are the major tectonic plates ?
- Antarctica and the surrounding Oceanic plate
- North American plate
- South American plate
- Pacific plate
- India-Australia-New Zealand plate
- Africa with the eastern Atlantic floor plate
- Eurasia and the adjacent oceanic plate
What are different types of plate boundaries ?
- Divergent plate boundary
- Convergent plate boundary
- Transform / Transcurrent fault boundary
What is a Transcurrent Edge / Conservative Edge / Transform Fault ?
Two plates grind against each other but there is no creation nor destruction of landform but just deformation of the existing landform. These faults are generally perpendicular to the mid-oceanic ridges
Which minerals (economically important) are found closer to the boundary of tectonic plates ?
Copper and Uranium
What is the Pacific ring of fire ?
The Ring of Fire is a region around much of the rim of the Pacific Ocean where many volcanic eruptions and earthquakes occur. It is 40,000 km long and up to about 500 km wide.
