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Uploaded by Angelicaromero16
GEOL101 Dynamics of the Earth – Spring 2023
Name: Angelica Romero
Laboratory 13: Geology through Google Earth
Section: 1003
Learning Outcomes:
●
Use Google Earth Pro to explore satellite data
●
Confirm your understanding of latitude and longitude
●
Describe changes in the Earth’s surface happening on human timescale
Background
Successful exploration and data collection on our planet depends on one’s ability to determine their current
position and identify their desired location. Over human history, different cultures developed various navigation
methods based on landmarks, astronomical features, magnetic compasses, and time-keeping devices. Today,
navigation is largely accomplished through remote reference to twenty-four signal-emitting satellites known as
the Global Positioning System (GPS) and locations are generally reported within the spherical coordinate system
of latitude and longitude. This spherical coordinate system is based on two basic components of our spinning
spherical (Figure 1): The first component is our planet’s rotational axis that intersects its surface at the north and
south geographic poles. The second component is the plane perpendicular to this rotational axis that is
positioned exactly halfway between the north and south geographic poles that is defined as the equator.
Latitude defines one’s north-south position, with
the equator defined as 0° and the geographic
poles defined as 90° N and 90° S. To visualize
latitude, imagine extending a straight line
downward from the city of New Orleans to the
center of the Earth where the equatorial plane and
rotational axis intersect (see figure to right). The
~39° angle formed by this straight line and the
equatorial plane defines the general latitudinal
position of New Orleans – literally how many
degrees the city is north of the plane of the
equator. If you were watching this latitudinal
position from space, the Earth’s rotation over 24
hours would trace out a circular path over the
planet’s surface that defines the ~39° N latitude
line. Longitude lines are also known as “parallels”
given their parallel nature and equally-spaced
orientation over the Earth’s surface. Note that the
circumference of latitude lines progressively
decreases from a maximum of ~40,075 km
maximum at the equator to single points at each
geographic pole.
Longitude defines one’s east-west position. To
visualize longitude, imagine extending 360
equally-spaced planes outward from the Earth’s rotational axis. The intersection of these planes with the Earth’s
surface would produce 360 lines of longitude that extend from pole to pole. Longitude lines are also known as
“meridians,” which is derived from the Latin meridiem (“noon”) given that local noon (i.e., when the sun reaches
its highest point in the sky) occurs simultaneously at all points along a given longitude line. These 360 longitude
lines are defined such that one of them passes directly through an engraved spot on the floor of the Greenwich
Observatory in England, and this specific line is defined as 0° longitude or the Prime Meridian. All other
longitudinal values are defined by the angle that their plane forms with that of the Prime Meridian along the
equator, and are reported as either “° W” or “° E” of the Prime Meridian (see figure above). The longitude line
opposite of the Prime Meridian is defined as 180° and is termed the International Date Line. Revisiting the city of
New Orleans, the nearest longitude line is 77° W - literally the number of degrees the city is west of the prime
meridian (Figure 1). Note that in contrast to latitude lines, all longitude lines are of equal length while the distance
between each progressively decreases as they converge toward each geographic pole.
Note that latitude and longitude positions can be more precisely reported by dividing each degree of latitude and
longitude into 60 minutes (1° = 60'), and dividing each of these minutes into 60 seconds (1' = 60"). Note that
minutes and seconds as used here refer to physical distances, not time units!
To explore latitude and longitude, open Google Earth Pro, type New Orleans into the search box in the upper left,
click the “Search” button to “fly” to New Orleans from wherever you currently are. Once you arrive, scan around
the city for the large white circle, which is the top of the Mercedes-Benz Superdome. Zoom in above the
Superdome to an altitude of about one kilometer, press “u” to remove any tilt in your view, click the push-pin icon
in the upper bar, place the pin in the middle of the Mercedes-Benz symbol, name the pin “Superdome,” and
record the latitude and longitude below including degrees, minutes, and seconds for each - be sure to North,
South, East, or West as appropriate!
1.
Center of Superdome in degree/minutes/seconds of latitude and longitude:
29°N /57 minutes /3.34 seconds
90°W/ 4 minutes/ 51.27 seconds
You can also express latitude and longitude with decimal values. Go to Preferences > 3D View and in the “Show
Lat/Long” box, select “Decimal Degrees.” Record the latitude and longitude below in decimals, being sure to
include North, South, East, or West as appropriate!
2.
Center of Superdome in decimal degrees of latitude and longitude:
29°57'3.34"N
90° 4'51.27"W
A super cool thing about Google Earth Pro is you can “go back in time” by looking at past satellite images of a
given area. Keeping your view centered on the superdome, click the clock face icon in the upper toolbar to reveal
a slider bar with different dates. By moving back in time, in roughly which year was the Superdome “rebranded”
as the Mercedes-Benz Superdome? Note you can click the little + and - magnifying glasses above the slider box
to go to finer and coarser time resolution.
3.
Year of Superdome rebranding:
2011
Now we’ll use latitude, longitude, push-pins, and the time slider to visit to jolly old England . . .
and see how some of it is washing away before their very eyes
Enter “Happisburg, UK” into the search box and travel
to Happisburgh is a small town in Norfolk County,
England. Zoom out to a distance of about 1,000 km so
you can see all of England and the location of the town
next to the North Sea. This town is experiencing
pronounced coastal erosion . . . in fact, an entire
hamlet once existed between Happisburg and the
North Sea. Unfortunately, the dominant rocks in this
area are unlithified loose layers of glacial till deposited
as glaciers receded from this region at the end of the
last ice age. Rising sea levels are now rapidly eroding
this material, causing the seacliff to migrate back
towards the town. Zoom into about 250 meters and
you should see a view somewhat larger than that
shown to the left. Notice the small push pin placed on
the westernmost crest of the church roof - you will use
this location as a reference point to measure seacliff erosion over time . . .
Note that the most recent satellite image is dated 10/2022 in the time-slider. Now go up to the command bar,
click “Tools” then “Ruler” to have a Ruler window appear in Google Earth. In the Ruler window, select the “Line”
tab and “meters” for the distance measurement. Now hover your cursor “crosshairs” over the western edge of the
roof church, click once to mark the spot, and then move your cursor “crosshairs” to the edge of the seacliff - try to
have your line show a 45° angle in the ruler box as this will make the line roughly perpendicular to the seacliff’s
edge. Once you get to the seacliff edge, click your cursor “crosshairs” again and read the distance in meters from
the church to the seacliff’s edge. Record this distance below . . . it should be roughly 122 meters. Note that the
dark back beyond the grass represents the shadow of the seacliff on the beach below - compare it to the shadow
of the church to help you identify the seacliff’s edge
4.
Distance in meters from the church to seacliff edge in October of 2022:
122 meters
Now use the time slider to go back to July 2009 and repeat your measurement from the church to the edge of the
seacliff in meters and record it below.
5.
Distance in meters from the church to seacliff edge in July 2009:
148 M
6.
What is the difference in distances?
26 M
7.
What is the difference in years?
13 years
8.
Calculate the average erosion rate of the seacliff in meters per year using the information in
Questions 6 and 7 above - be sure to include your units in your answer.
26 M/ 13 yrs = 2 M/ yr
9.
Assuming the erosion rate above continues and given the 2022 distance from the church to the
seacliff, roughly how many years does the church have until the church itself is at the edge of the
seacliff?
It would take about 60 years for the church to be at the edge of the seacliff/
10. Ongoing global warming is causing the melting of glaciers and the thermal expansion of sea
water – both contribute to a documented global rise in sea level. Given this, what do you think
about your estimated number of years in Question 9 above? Is it more likely an overestimate or
an underestimate? Why?
I think the number is an underestimate because erosion is happening at such a fast pace due to
the cliff being made from boulder clays that are less resistant, therefore causing the church to be
pushed to the edge sooner.
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