GEOL101 Lab 2 Handout
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San Diego State University *
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Course
101
Subject
Geology
Date
Feb 20, 2024
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5
Uploaded by ChancellorMask13509
GEOL101 Dynamics of the Earth – Fall 2023
Name:
Lily Razzano
Laboratory 2:: Geology through Google Earth
Section:
GEOL101 Lab
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:
DMS: 29° 57' 03'' N , 90° 04' 51'' W
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:
Latitude: 29.951439
Longitude: -90.081970
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:
2021
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 “Happisburgh, 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:
126.94 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:
139.63 meters
6.
What is the difference in distances?
12.69 meters
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.
.9762 meters per year
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?
About 130 years
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
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you think about your estimated number of years in Question 9 above? Is it more likely an
overestimate or an underestimate? Why?
I believe the estimated number is an overestimate because roughly 1 meter of erosion per year
is a rapid rate and with additional rates of global warming and other added factors that number
will definitely increase throughout the years to come.
Latitude Longitude Practice
11.
Using the simple Lat-Long map provided below please give the latitude and Longitude of
the following places in two formats (extrapolate to the nearest degree)
a. Buenos Aires (-34, +58) (34S, 58W)
b. Rome
(40 , 15) (40N , 15E)
c. Melbourne
(-40, 140) (40S , 140E )
d. New York City
(40, -70) (40N , -70W)
e. Southern Tip of Greenland
(60, -45) (60N , 45W)
e. Southern tip of Japan
(
30 , 130) (30N , 130E)
f. Southern Tip of India
(10 , 80 )
(10N , 80E )
g. New Zealand (center of north Island)
(-45 , 165 ) ( 45S , 16SE)
12.
The Earth rotates 15 degrees every hour, so what is the time difference (in hours)
between Melbourne and Buenos Aires?
Melbourne is 13 hours ahead of Buenos Aries