View (Geography) (Fold Mountains)
Thursday, October 20, 2011
Monday, October 17, 2011
Density (3.0) Heavier
Density (2.6) Lighter
30-70 km thick
6-10 km thick
<200 million years old (younger)
>1,500 million years old (older)
Aluminum,granite,silicon and oxygen
Sunday, October 16, 2011
What are the difference between plates made of oceanic and continental crust?
A continental plate is much lighter in density. It is thicker and therefore "floats" higher on the mantle and is above the ocean level. The oceanic plates are denser, less felsic, and are thin and are generally covered by the ocean. Continental plates are generally older. Oceanic plates tend to get subducted beneath other plates. During the process of subduction, lighter material is sometimes forced up with magma that may add substance to the continental plate.
What are the difference between destructive and constructive plate margin?
At a constructive (divergent) plate boundary, new crust is being created to infill the gaps caused by spreading plates. At a destructive (subduction-convergent) plate boundary, old, dense oceanic crust is diving into, and becoming part of the mantle
How is a conservative margin different from those two?
A conservative margin does not create nor destroy. It only moves side by side in the same or opposite direction. Unlike constructive and destructive margins, no volcanic activity occurs here. Although, earthquakes do happen when pressure builds up on the plates.
Monday, October 3, 2011
KEY words: lithosphere,convergent,(destructive)divergent (constructive),conservative
-Boundaries don’t move in the same direction
-Plates are divided into the continents they resides in
-North American plate seems to be the biggest
-Juan De Fuca plate is the smallest
-Some plates are completely oceanic, some are a mix of oceanic and continental plates
-Some plates have trenches
-some plates have ridges
Red: Where plates meet
What are PLATE BOUNDARIES?
Found at the edge of lithosphere
where tectonic activity takes places
3 types of plates
Hello today I’m going to talk about one of the most extraordinary theory that seem to have shattered the geographic community, the continental drift theory. Proposed by Alfred Wegener, the theory stated that the earth was once a super continent called Pangaea and then over time the continents seemed to have drifted apart to their current places due to millions of years of tectonic activity. At first the geographic community disagreed with the theory but then convincing evidence was dug up by Alfred. He found out the dinosaur Mossasaurs was found out on opposite sites of the world, also he discovered that similar animal and plant species were found on different sides of the world. If that evidence was not convincing enough, he discovered that the continents could fit together like a big jigsaw. Plus, there was more evidence with similar chalk samples found from mountains in the UK and France. Lastly, glacial has been found on countries like Africa and this proves that Africa was always not near the position where it was supposed to be and it drifted from somewhere near the colder regions. Sadly, this still was not enough to convince the community in Alfred’s time but now it has become a generally accepted theory in the geographic community.