Lecture Quiz 2 Flashcards
the half life of a radioactive element is
the time required for half the parent to decay to the daughter
a plate boundary where the plates are moving away from each other is called
divergent
a surface in a vertical sequence of rocks where time is not represented by rock is called
unconformity
calderas or supervolcanoes are very dangerous because
the magma is very silica rich, the amount of ash erupted would be very large, the eruption would be regional
igneous rocks typically form at and volcanic activity takes place at
convergent boundaries, divergent boundaries, mantle hot spots
the most dangerous process associated with composite cones in close proximity to coastal cities is
mud flows
earthquake magnitude
is measured on the Richter scale, is calibrated for distance
most of the structural damage from earthquakes is caused by
surface waves
p waves travel through all types of materials and are transmitted via
compression
three sites (L1 L2 L3) record earthquakes intensity and earthquake magnitude for the same earthquake. L1 is located closest to the earthquake focus, L3 is farthest away. the intensity values are greatest at _____ and the earthquake magnitude(calculated using seismograms) _____
L1; is the same at each site
the slopes of a shield volcano are not as steep as a composite cone because
the lava is less viscous
seismic waves particularly body waves give us a great deal of information about the interior of the earth, and in fact we know that the outer core is a liquid because
S waves disappear
wegener’s idea of continental drift was rejected because
although he had plenty of evidence, it lacked a suitable mechanism
A tectonic plate boundary in which the plates are moving towards the boundary commonly destroying oceanic crust and generating intermediate magma that rises to become stratovolcanoes/composite cones
ocean continent convergent, subduction zones, ocean ocean convergent
melting the material that will become magma and eventually igneous rocks and volcanic activity inloves
bringing heat up with convection, taking the crust deeper with subduction
the main driving force that results in the movement of the crustal plates is
mantle convection
although it was a much smaller event, the earthquake in Haiti resulted in much greater numbers in terms of loss of life than in Chile because
building design, lack of building codes
cone shaped volcanoes occur because
volcanic ash has a high angle of repose, the magma is more viscous
the driving force behind a volcanic eruption, or the process that forces magma out of the ground
gasses bubbling out of solution
volcanic eruptions can change climate because
volcanic ash in the atmosphere blocks in the sun
the overall explosive nature of a volcanic eruption can be predicted by
the amount of silica in magma
stratovolcanoes form as______ build up over time
alternating layers of ash and viscous lava
the modern evidence for plate tectonics includes
the geography of the oceans, the geographic distrution of earthquakes and volcanoes, the age of the sea floor
earthquakes that occur near coastal areas can be very destructive because
liquifaction can occur, tsunamis can occur, water saturated sediments amplify seismic waves
tsunamis occur when
earthquakes occur on the ocean floor
stratovolcanoes form at
convergent plate boundaries
geologically speaking a mountain is where the
crust is thicker
the geologic time scale is
a calender of earth history, hierarchal, combines the two frameworks of geologic time
geologists know that volcano is about to erupt if
the shape of the mountain changes, composition of gasses coming from volcano changes, there are numerous small earthquakes
most mid ocean ridges (ocean ocean divergent plates boundaries) begin as
continent continet divergent plate boundaries, continental rifts
what are some examples of the modern evidence for plate tectonics, and how is it different from continental drift?
earth quakes, volcanoes,
plate tectonics happen because of sea floor spreading, contentiental drift does not.
what is the driving force for a volcanic eruption, and why are some volcanic eruptions more explosive than others
driving force is gasses building up
they are more explosive becuase of the silica in the magma it determines the viscosity
what was not typical about the May 18, 1980 eruption of Mount St. Helen? what were some of the warning signs that this mountain was about to erupt?
the mountain blew out the side, warning signs were the change in the weather, it got all dark in the sky
why was Wegener’s idea of the continental drift rejected,and what was some of the evidence that he had that the continets had drifted into their present position?
it was rejected because floating continets, movement by centufugal force, aninadwquate mechanism.
evidence- jigsaw fit of the continet’s edge, paleoclimate indicators at wrong latitudes, glacial deposits (till and striations)
