Lesson 10: Paleogeography and Plate Tectonics Flashcards
Who was Alfred Wegener?
a German researcher in 1912
noticed that the eastern coastline of South America and the western coastline of Africa looked like two connectable puzzle pieces
that the fossils of many ancient animals could be found in both South America and Africa
several geologic formations in South America had seemingly identical twins in Africa
suggested that Africa, South America and possibly other continents had once been connected and had since drifted apart
What was the flaw in Wegener’s theory?
he could not offer a convincing mechanism for how land masses as big and as seemingly immobile as continents could move
What is the crust?
the outermost layer of the earth
consists of the continents and ocean basins
the thickness of the crust varies but is usually between 5 and 25 kilometers deep
What is the mantle?
a layer over 2,500 kilometers deep
although it flows, the mantle is not a liquid, but a viscous solid that flows
the intense heat and pressure at great depths causes the solid mantle to behave like a fluid
similar to play-doh that is solid at rest, but that squishes when you squeeze it
What is the lithosphere?
the solid uppermost portion of the mantle
is not one unbroken layer, but is actually composed of many discrete pieces, or plates, that fit together
What is the asthenosphere?
part of the mantle below the lithosphere
viscous, slowly flowing, and its shape may be deformed under the uneven weight of the lithosphere
the extreme heat of the inner layers of the earth creates convection currents in the viscous asthenosphere
lower portions of the asthenosphere slowly heat, expand, rise upwards, and then slowly cool and sink
What is the core?
the core is primarily composed of iron and nickel and is subdivided into the outer core and inner core
What is the outer core?
comprised of molten liquid
What is the inner core?
is a solid ball
the temperature of the inner core is estimated to be roughly 5,700 degrees Celsius (the same as the surface temperature of the sun)
What are plates?
pieces of the lithosphere, are affected by convection currents in the asthenosphere
the currents pull along the undersurfaces of the lithosphere’s various pieces, causing them to slowly move
What is plate tectonics?
the cool crust is more solid and dense than the layers below it
this causes lithosphere plates to slowly sink and to melt into the lower layers
this sinking does not happen all at once, but occurs gradually along one of the edges of a plate
as one edge sinks, a small gap is created along the opposite edge, and, through this gap, molten rock is free to escape
this rock then cools, solidifies, and adds its own mass to the edge of the plate
this cycle continues and, ever so slowly, the newly erupted rock will eventually progress to the sinking edged and be melted once more
What are mid-ocean ridges?
the discovery of mid-ocean ridges revealed plate edges where new crust was being formed
studies of mid-ocean ridges show that the crustal rocks on either side of the ridges have indeed been slowly drifting apart
advanced global positioning satellites tracking systems can detect the ongoing movements of the continents and even record their speeds
How do different plates interact with each other?
as plates move, they sometimes come into conflict and collide
the boundary where two plates collide can be a place where tremendous pressure builds
such plate boundaries are often sites of sudden pressure releases, in the form of volcanos and earthquakes, and/or of gradual pressure releases, which can slowly build mountain ranges
What was Pangaea?
by the end of the Permian period and the beginning of the Triassic period, all the world’s continents had collided together and formed the single supercontinent Pangaea
because Pangaea was a single unbroken land mass, the first dinosaurs that appeared during the Triassic were able to spread across the entire planet, with no major sea barriers standing in their way
for this reason, during the late Triassic and early Jurassic, dinosaurs all across the world are fairly similar
prosauropods and small theropods similar to Coelophysis are found worldwide
What was Panthalassa?
all the world’s oceans were also one
single super-ocean
What are the characteristics of the diplodocids?
among the thriving Jurassic long-necks
even compared with other sauropods, most diplodocids have extremely long necks
they are also characterized by front legs that are much shorter than their hind legs, and by their unusual faces
the skull of a diplodocid is elongated and resembles the general shape of a horse’s or a deer’s
diplodocid teeth are simple, peg-like, and are positioned only at the front of the mouth, not on the sides
they are nipping teeth, good for cropping off leaves and other tender growth
What are the characteristics of the macronarians?
group of sauropods in the Jurassic
do not have the whip tails of diplodocids
their bodies are generally more robust, and their front legs are usually not noticeably shorter than their back legs
macronarians like Brachiosaurus and Giraffatitan the front legs were much longer than the back legs
most still have the long necks characteristic of sauropods, and they too filled the ecological niche of high browsers
