Ch2 Flashcards
New oceanic crust and lithosphere are formed at
Divergent boundaries by submarine eruptions and intrusions of basaltic magma
The ___ are a logical evolutionary a analog of the Africa rift valleys ten million years from now
Red Sea
Volcanoes and deep valleys of east Africa are related to a
Continental rift along which parts of the African continent are beginning to slowly separate
Which if the following most accurately describes the volcanoes of the Hawaiian islands
Shield volcanoes fed by a long lived hot spot below the pacific lithospheric plate
The temperature below which magnetic material can retain a permanent magnetization is called the
Curie point
The Aleutian Islands occur at a
Convergent boundary on a volcanic arc above a northward subducting Pacific plate
The__ is an example of an active, continent-continent collision
Northward movement of India into Eurasia
Deep focus earthquakes are associated with___ plate boundaries.
Convergent (subducting)
A transform plate boundary is characterized by ___
A deep, vertical fault along which two plates slide past one another in opposite directions
A typical rate of seafloor spreading in the Atlantic Ocean is
2 cm per year
A very long lived magma source located deep in the mantle is called a ___
Hot spot
All of following contribute evidence supporting the theory if plate tectonics except for __
Changes in the moons orbit due to shifting plates
Deep ocean trenches are surgical evidence for ___
Sinking of oceanic lithosphere into the mantle at a subduction zone
Deep ocean trenches are most abundant around the rim of the ___ ocean basin
Pacific
Cooler, older, oceanic lithosphere sink into the mantle at ___
Subduction zones along convergent plate boundaries
The continental drift hypothesis was rejected primarily because Alfred Wegener could not ___
Identify a mechanism capable of moving continents
Pull apart, rift zones are generally associated with
Divergent plate boundary
Linear, magnetic patterns associated with mid ocean ridges are configured as
Normal and reversed magnetized strips roughly parallel to the ridge
Which one of the following is an important fundamental assumption underlying the are tectonic theory
Earths diameter has been essentially constant over time
___ plate boundaries have the larger magnitude earthquakes
Transform and convergent
In the early part of the 20th century, ___ argued forcefully for continental drift
Alfred Wegener
On average, lithospheric plates ___ thick
100km
Where would you drill to recover samples of the oldest basalts of the oceanic crust, which are Jurassic in age?
Oceanic side of the Aleutian trench, along the southern coastline of Alaska
___ most effectively outlines the edges if the lithospheric plates
Iines of earthquake epicenters
___ first related the symmetrical magnetic patterns in seafloor basalts to seafloor spreading at a mid ocean ridge
Vine and Matthews
The ___ were formed in the late Paleozoic when sediments in a marine basin were squeezed and crumpled between converging continents
Urals in Russia
Mount St. Helens and the other cascade volcanoes are ___
Young, active volcanoes built on a continental margin above a sinking slab of oceanic lithosphere
T or f: during the geologic past, the magnetic poles have generally been very close to earths geographical poles
True
In general, rocks of the continental crust are less dense than rocks of the oceanic crust
True
In general, seafloor sediments gradually thicken away from a mid ocean ridge
True
As the south Atlantic basin widens by seafloor spreading, Africa and South America are moving closer together
False
