Science Chapter 11
Terms in this set (69)
the idea that the continents move around on Earth' surface
who was Alfred Wegener?
a german scientist and arctic explorer who suggested the concept of continental drift
an ancient, huge landmass composed of earlier forms of today's continents; an ancient supercontinent
the study of lithospheric plates; a theory explaining how the pieces of Earth's surface (the plates) move
evidence for the continental drift
matching plant, mammal, and reptile fossils; matching coal beds, rock patterns, and mountain ranges; glacial evidence in warm areas; shapes
was the continental drift rejected? why?
yes because there was no evidence of the mysterious force that caused the continental drift
who was harry hess?
an american geophysicist and naval officer whose work helped develop the theory of plate tectonics
a long chain of undersea mountains
a hypothesis that new sea floor is created at mid-ocean ridges and that, in the process, the continents are pushed apart from eachother
evidence of sea-floor spreading
magnetic patterns and the age of rocks
where were oldest rocks located on the ridges?
farthest from the ridge
where were newest rocks located on the ridges?
closest to the ridge
large pieces of Earth's lithosphere that move over the asthenosphere
what do lithospheric plates move over?
two kinds of lithospheric plates
oceanic and continental
thin lithospheric plates that form on the ocean floor and are made of basalt, denser that continental plates
thick lithospheric plates that are made of andesite and granite and form the continents, less dense than oceanic plates
what questions do plate tectonics answer
why volcanoes and earthquakes are where they are and where we can find oil, gas, gold, and other important resources
what drives the lithospheric plates?
convection cells in the lower mantle
what happens at mid ocean ridges
the lower mantle rock material rises towards the surface, basaltic lava is extruded between the plates along the mid-ocean ridge, and the lava adds to the plate's size
a process that involves a lithospheric plate sinking into the mantle
what happens when an oceanic plate meets with a continental plate?
the oceanic plate will subduct under the continental plate
heated lower mantle rock that rises toward the lithosphere because it is less dense than surrounding mantle rock
what type of activity can be found at mid-ocean ridges
what can a single, hot, rising mantle plume sometimes cause
a volcanic eruption
what happens if the mantle plume eruption is strong and lasts long enough
the volcanic eruption may form an island on the plate
what is the first island in the island chain made of
old, dormant volcanoes
what is the last island in the island chain made of
how do scientists determine the direction and speed of plate movement?
measuring the island chains
what is a good example of an island chain from by a mantle plume hot spot?
the Hawaiian Islands
three plate boundaries
divergent, convergent, transform fault
divergent boundary diagram
convergent boundary diagram
transform fault boundary diagram
types of divergent boundaries
mid-ocean ridges and rift valleys
where are divergent boundaries found?
over the rising part of a mantle convection cell
what causes the two plates to move away from each other at a divergent boundary?
what happens when a rift valley forms on land?
it may eventually split the landmass wide enough so that the sea flows into the valley and the rift becomes a mid-ocean ridge
what is an example of a divergent boundary on land?
the East African Rift Valley
types of convergent boundaries
deep-ocean trenches, mountain ranges and possibly volcanoes
when does a deep-ocean trench form?
when two oceanic plates collide and one plate subducts under another
why does one plate subduct under another?
because a denser plate subduct under a less dense one
what type of ocean plate is cooler and denser?
an older oceanic plate
what type of ocean plate is less dense?
a young oceanic plate
what happens if an oceanic plate and a continental plate collide?
the oceanic plate will subduct under the continental plate
what is an example of an oceanic plate subjecting under a continental plate?
the Nazca Plate subducting under the South American Plate
what happens when an oceanic plate with a continental plate attached is subjected under another continental plate?
eventually all of the ocean crust is subjected and the continental plates collide
what do colliding continents form? give an example.
they form mountains (for example the Himalayan Mountains)
what two plates colliding caused the Himalayan Mountains to form?
the Indo-Austrailian Plate moving towards the Eurasian plate
evidence of a transform fault boundary
zig-zag patterns (offsetting), slickenslides, and earthquakes
example of a transform fault boundary
the San Andreas Fault
what does the San Andreas Fault separate?
the Pacific and North American Plate
at what boundaries do earthquakes occur
convergent, divergent, and transform fault
at what boundaries does volcanic activity occur
convergent and divergent
what are slickensides
polished rock surface that is evidence of plate boundaries
slides objects past each other
pulling force applied to an object that can make an object stretch
the force generated from compressing an object or substance
how many lithospheric plates are there
7 major ones
what are the lithospheric plates
Pacific Plate, American Plate, Nazca Plate, African Plate, Eurasian Plate, Indo-Australian Plate, and Antarctic Plate
which plate is more bouyant?
what happens when two oceanic plates collide?
the older oceanic plate will subduct under the younger oceanic plate and a trench and/or a volcano will form
what happens when two continental plates collide?
what are continental plates made of?
andesite and granite
what are oceanic plates made of?
where are the newest parts of earths crust located?
mid ocean ridge
what 3 characteristics determine whether one plate will subduct under another?
age, density, and type of plate (oceanic or continental)
why are magnetic reversal patterns important?
because it shows expansion
how does convection work?
magma is pushed upwards through the ridge cracks by convection currents, As some magma erupts out through the crust, the magma which does not erupt continues to move under the crust with the current away from the ridge crest and it moves the plates and ocean floor