exam 3 Flashcards
seismic waves
generated from the breaking of the earth’s crust (earthquakes) used to learn about the earth’s interior
surface waves
move along the outside of the earth
body waves
travel through the earth and are changed by the contents of the interior, they are reflected, refracted, or absorbed
inner core
solid made of NI and Fe
outer core
liquid made of Ni and Fe
lower mantle
makes up the most volume, solid made of silica
asthenosphere
plastic layer below the crust
continental crust
2.7g/mL, 25-50 miles thick
oceanic crust
3.0g/mL, 2-4 miles thick
mt everest
earths highest point, 29,028ft
denali
highest point in North America, 20,320ft
challenger deep
lowest point of the Marianna’s trench 36,000ft
shrinking earth model
1600s-1900s thought the earth’s topography was formed by decreasing the earth’s volume while keeping the surface area the same; debunked because there are not uniform wrinkles
sir francis bacon
proposed continental drift when he noticed the coastlines of the continents look like they would line up in the 1620s
alfred wegner
proved the existence of pangea by matching up the rocks and fossils on the coast of Africa and South America in the 1910s
Arthur Holmes
proposed sub crustal convection as a mechanism for continental drift requiring a liquid under the crust in the 1930s
sonar
used to map the ocean floor topography, first map produced in 1959
bathymetry
mapping ocean floor topography
direct observation
stronger submarines allowed us to observe ridges and note effusive volcanos along the MORs
geography of earthquakes
set up arrays of seismometers in response to the cold war that allowed us to create an earthquake map
absolute age dating
of oceanic floor rock via deep sea drilling projects showed that the youngest rocks are around the MOR and older rocks are along the continents
glomar ships
used to collect oceanic rocks for absolute age dating
first complete map of the earth’s surface
1977
Harry Hess
proposed sea floor spreading for creating new oceanic crust in the 1960s
subduction
destroys oceanic crust at the coasts, crust is constantly recycled oldest is only 226myo
plate tectonics
a number of distinct mappable plates move spatially an average of 6cm a year up to a max of 18cm a year
isostacy
vertical bobbing of tectonic plates as the mass of the continents changes
divergent boundaries
most occur in the oceans along MOR via sea floor spreading, shallow minor earthquakes
east african rift valley
divergent valley on land
convergent boundaries
locations where plates collide that differ based on conditions
oceanic - continental covergence
subduction of sima under sial creates an oceanic trench and volcanoes on the coast, strong deep earthquakes
oceanic - oceanic convergence
one side will slip under the other creating a trench and a volcanic island arch, strong deep earthquakes
continental - continental convergence
uplift creates a nonvolcanic mountain range, strong shallow earthquakes
transform boundaries
plates slide past each other creating a high volume of earthquakes
Hawaii
has a straight volcanic chain in the middle of the ocean contradicting what we know, only the youngest volcano is active
mantle plume
isolated body that is hotter than the rest of the asthenosphere and is fixed in place creating a hotspot which makes a weak point in the crust for magma to seap out
verbal scale
a sentence for example 1 inch equals 495 miles on the globe
bar scale
a measurable representation of map scale
representative fraction (RF)
map distance over earth distance representation given as either a ratio or a fraction giving unit to unit conversions
features found on all maps
title, northern orientation, scale, source or reference,
standard US map
a 7.5 minute topographic quadrangle
topographic maps
show the elevation of the earth’s surface using contour lines
isolines
connect points of equal value on a map
closely spaced contour lines
a steep slope
widely spaced contour lines
a gentle slope
coordinate systems
grid systems that help determine geographic location
elevation
vertical distance above msl
latitude
based on relative angle to the north star, divided into hemispheres by the equator; lines are called parallels
longitude
based on time zones, all meridians converge at the poles, prime meridian and international date line divide the earth
Greenwich England
arbitrary point deemed as longitudinal 0, location of the prime meridian
distance between degrees of latitude
69 miles
1 degree
60 min, 3600s
true north
geographic north, 90 degrees latitude, differs from magnetic north
magnetic north
point in northern Canada where there is a magnetic pole which wanders over time requiring adjustments to maps
magnetic declination
difference between magnetic and true north given in a degree and east or west direction
magnetic declination in ship today
11 degrees west
pole flip
last occurred 780000 ybp
hatchures
represent closed depressions or bowls on a map with hatched contour lines
brown on a map
indicates contour lines
blue on a map
indicate hydrographic features, contour lines point upstream
red and black on a map
transportation routes or buildings
purple on a map
map revisions since the previous edition
light red on a map
urban areas where buildings are too close together to be mapped individually
