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
What is an ecological niche?
a niche is an animal’s way of life
think of it like the animal’s job in the ecosystem, it’s how a particular species makes its living, what it must do to survive
What is niche partitioning?
the process by which natural selection drives competing species into different patterns of resource use or different niches
What are the characteristics of the thyreophorans?
group of smaller Jurassic herbivores
includes the ornithischians with body armor
most well-known is the Stegosaurus
fossils have been found in Africa, Asia, Europe, and North America
What are the characteristics of the allosauroids?
were different from the big predators that had come before them
have vertebrae that interlock more rigidly, so their spines were held stiffer
their legs are also proportionately longer, suggesting that they were faster than either megalosaurids or ceratosaurids
What are the characteristics of Coelurosaurs?
characterized by a long series of sacral vertebrae, narrow hands, and tails with back halves that are skinny, stiff, and lightweight
spawned the dinosaurs’ greatest success: birds
in the Cretaceous, some coelurosaurs would evolve their way to the very top of the food chain
What was Laurasia?
was northern of the two sections of Pangaea
was composed of what we today call North America, Europe, and Asia (excluding India)
What was Gondwana?
was the southern of the two sections of Pangaea
and was composed of what we today call South America, Australia, Africa, Antarctica, Madagascar, and India
What dinosaurs were present in North America and Europe in the Early Cretaceous?
iguanodontians, ankylosaurs, and branchiosaurid sauropods
What dinosaurs were present in Africa in the Early Cretaceous?
spinosaurs and carcharodontosaurids
What dinosaurs were present in Asia in the Early Cretaceous?
coelurosaurian theropods became common, and the first ceratopsians evolved
What are the characteristics of Titanosaurs?
are the most robust of all sauropods
their chests are broad and their hips are wide
their hind limbs are spaced far apart, giving them a very stable base
many had osteoderms and some even had large spikey armor
ranged in size, but but among their ranks were animals like Argentinosaurus
What are the characteristics of Carcharodontosaurs?
are named for the shape of their teeth
are a type of allosauroid, so they are descendants of the big theropods the first rose to prominence in the Late Jurassic
have bigger heads, with longer jaws
What are the characteristics of Abelisaurs?
were the last survivors of the ceratosauroid lineage, and some grew to over eight meters in length
in the Cretaceous, the group was strictly limited to Gondwana, but they evidently thrived there, as abelisaur fossils have been found throughout the southern hemisphere
What are the characteristics of ankylosaurids?
the ankylosaurs with the famous tail clubs
also typically have large backwards-pointing horns at the rear of their skulls and a short rounded snout at the front
What are the characteristics of nodosaurids?
they lacked tail clubs, but some have offensive weapons at the other end, in the form of large osteoderm spikes that project outwards from over their shoulders
do not generally have the big skull horns of anklosaurids, and their snouts are significantly narrower and more elongated
What are the characteristics of lambeosaurine hadrosaurs?
had a big crest on their heads, which can be played like a musical instrument
inside a lambeosaurine crest is a complex and hollow nasal passageway
blowing air through this passage and then out the nostrils would have amplified the dinosaur’s calls
the hollow crests come in a variety of shapes and sizes
What are the characteristics of hadrosaurines?
they do not have the complex sound amplifying crests of the lambeosaurines
however, some do still have crests
What are the characteristics of marginocephalians?
name literally means “fringe heads” and refers to an overhanging lip of bone at the back margin of the skull
pachycephalosaurs and ceratopsians are major groups
What are the characteristics of ornithomimids?
are a kind of coelurosaur that evolved a body plan similar to that of a modern ostrich or emu, but with long clawed forelimbs and a large tail
What is a semilunate carpal?
specialized wrist bone
these crescent-shaped bones allowed the hand to be folded backwards at a sharp angle, and the dinosaurs that posses them are called the maniraptorans
What are the characteristics of maniraptorans?
birds are one group of them, and the semiluate carpals of birds allow them to delicately fold their wings when not flying
What are the characteristics of oviraptorosaurs?
a group of therapods that adapted to a mostly vegetarian life and lost their teeth in favor of large beaks
many oviraptorosaurs had cranial crests and fans of feathers on the ends of their tails
What are the characteristics of therizinosaurs?
strangest of all Laurasian coelurosaurs
first fossil to be found was a huge claw, over 60 cm
have small skulls on the end of long necks and hind feet with four forward pointing toes
have a backwards-directed pubis and jaws with small herbivorous teeth in the back and a beak in the front
What is faunal interchange?
the movement of the continents does not always lead to geographic isolation - sometimes, plate tectonics brings continents that were once separate back together
when this happens, dinosaurs from one region can move into another, leading to similar species in both regions
In what ways was the global climate in the Age of the Dinosaurs different then now?
temperatures were, on average, much higher
this warmer global climate was largely caused by high volcanic activity, which released large quantities of carbon dioxide into teh atmosphere
the concentration of all Earth’s land masses in only one or two supercontinents may have also been a factor that contributed to the high average temperatures, because it affected the circulation of both air and water currents through the polar regions
What were the sea levels like in the Mesozoic?
sea levels were up to 250 m higher than they are today
this resulted in the flooding of vast regions of the earth, limiting the amount of exposed land and splitting areas that are now connected into isolated islands
