Lab2_Volcanism celeste
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Department of Geography, Environment and Geomatics
GEG2301: Geomorphology
Lab 2: Volcanic Landforms and Processes
Due date: October 6
th
before 16:00 on Brightspace
This lab aims to introduce you to different types of volcanic landforms. You will use Google
Earth to fly to locations, and describe and explain the formation of these features.
Note:
a)
You must use the standalone version of Google Earth Pro (not one embedded within a
web browser)
b)
Please answer all questions directly in this document and upload the assignment in PDF
format
c)
No late assignments will be accepted
First, open Google Earth Pro. Then, in the top toolbar select Tools -> Options and in the 3D
View tab set the
Elevation Exaggeration to 2
and ensure that the ‘
Use high quality terrain
’
and ‘
Use 3D imagery’
boxes are both checked.
Using the
Firefox
or
Google Chrome
browser (
NOT
Internet Explorer), click on the
‘Volcanism_lab.kml’ file provided on Brightspace to open it in Google Earth.
Location 1
:
Big Island, Hawaii
Open the “Big Island, Hawaii” folder and double-click the ‘A’ placemark to fly to it.
1.
Study the dark material spread along the slope near location A. What is the name of this
feature and what kind of rock is it made from (igneous, metamorphic or sedimentary)? (2
marks)
This feature is a volcano and the rock it is made out of is igneous.
2.
Describe why the colour of the material at location A is very dark (2 marks)
It is very dark because it forms from the solidification of molten lava that has erupted
from the volcano.
3.
Where did the material at location A originate from? Provide evidence to support your
statement (2 marks)
The material originated from lava flows that have occurred when molten rock (lava)
erupts from a volcano and flows down the slopes.Over time, the lava cools and solidifies,
forming the dark rock that we see.Since the material is located at the slope of a volcano,
it easy to conclude that it originated from volcanic eruptions.
4.
List the relative ages of Placemarks A to C (from youngest to oldest), and discuss the
evidence for your interpretation (3 marks)
The ages of rock under placmark A would be younger because of the recent lava flow that has
formed new igneous rock. The rocks under C being the oldest, could be older igneous rock from
larger eruptions or runoff from pass Laval flows.
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5.
Placemarks D and E indicate two examples of a distinctive volcanic feature. What is the
name of this feature, and how is it formed (2 marks)?
These are cinder cone volcanos and are formed during eruptions when pyroclastics (rock
fragments) discharged.
6.
Zoom out so that you can see the entire Hawaiian Island chain (placemarks A to F). Sketch
the distribution of the islands below and mark which is the oldest and newest (Draw free
forms and add text boxes in the space below using the drawing tools of your word
processor. The sketch is approximate, but must include a scale). Describe how these islands
formed, and how their distribution and age relates to plate tectonics (4 marks)
The geological phenomena of hotspot volcanism, which is intimately related to plate tectonics, is
what caused the Hawaiian Islands to form. A continuous series of volcanic islands was formed
by molten rock ascent through the Pacific Plate, which was made possible by a fixed hotspot in
the Earth's mantle. The Big Island is the youngest of these islands, whereas the islands to the
northwest get older with time. This age progression results from the west-northwest migration of
the Pacific Plate. The interaction between plate tectonics and volcanic processes in determining
the distribution and age of the Hawaiian Islands is demonstrated by the erosion and subsidence
that occurs to islands as they migrate away from the hotspot, leading to their eventual
transformation into atolls or seamounts.
7.
What is the likely strength of large volcanic eruptions in Hawaii? Provide evidence to support
your statement (3 marks)
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Although the intensity of large volcanic eruptions in Hawaii might vary, they are often
characterised by mild explosivity in comparison to certain other volcanic locations. The basaltic
character of the lava that is frequently seen in Hawaiian volcanoes serves as proof for this. In
contrast to andesitic or rhyolitic lava, basaltic lava is less viscous and gas-rich. Due to the low
viscosity of the magma, explosive explosions are less likely since gas may exit the magma
relatively easily. Instead, Hawaiian volcanoes frequently experience effusive eruptions, in which
lava gently flows from fissures or vents, resulting in more controlled and subdued volcanic
activity.
8.
Placemark G indicates Osorno Volcano in Chile. Describe how the steepness of this volcano
compares with the large volcanoes in Hawaii (Placemark A), and explain the reasons for it (3
marks).
The Osorno Volcano in Chile, indicated by placemark G, is most likely to have the steep, conical
form that stratovolcanoes are known for. These volcanoes' steep slopes are a result of the
layers of volcanic material that have accumulated there throughout time. On the other hand, the
enormous volcanoes of Hawaii, such the ones indicated by placemark A, have a different profile.
These shield volcanoes are distinguished by their wide, gently sloping slopes. In Chile,
stratovolcanoes tend to be steeper due to their explosive eruptions and the accumulation of
materials, whereas Hawaiian shield volcanoes have gentler slopes due to their effusive
eruptions and the widespread flow of less viscous lava. This difference in steepness results from
the different volcanic types.
9. What kind of plate tectonic boundary occurs in Chile around Osorno Volcano, and how would
you expect the colour and density of rocks produced by this volcano to differ from those in
Hawaii? (3 marks)
There is a convergent plate tectonic boundary at the Osorno Volcano in Chile, where the South
American Plate is being subducted beneath the Nazca Plate. In this tectonic environment,
stratovolcanoes like Osorno are formed. The andesitic to dacitic volcanic rocks that Osorno
produces often have intermediate colours like grey to light brown. In contrast, the Hawaiian
volcanoes produce basaltic rocks that are mostly deeper in colour, often black or dark grey, due
to the divergent plate boundary they have created over the Pacific Plate hotspot. Furthermore,
the higher viscosity of andesitic and dacitic magmas in Chile results in usually denser volcanic
rocks, whereas low-viscosity basaltic lavas in Hawaii produce less dense volcanic materials.
Location 2: Shiprock, New Mexico
Open the “Shiprock, New Mexico” folder and double-click on it to fly there.
8.
What is the feature seen at location H? How was it formed? (3 marks)
A monadnock, or isolated hill, may be found at point H. Dikes and volcanic rocks make up its
structure. Dikes are almost vertical intrusions that are created when cracks or splits are filled. It
originated from a volcanic explosion that caused layers of volcanic material to build up.
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9.
What are the features at I and J? Describe their orientation compared to the surrounding
bedrock (2 marks).
A pluton is this feature. In relation to the nearby bedrock, plutons can have varied orientations.
Discordant plutons cut across these characteristics, whereas concordant plutons intrude parallel
to the present layering or foliation of the host rocks. Geological elements including tectonic
forces and the structure of the magma chamber can affect a pluton's orientation.
10. What is the summit elevation of Shiprock, and what is its height above the surrounding
plain? (2 marks)
Shiprock, New Mexico, has a top elevation of around 7,177 feet (2,187 metres) above sea level.
It rises considerably over the plain in its immediate vicinity, rising about 1,587 feet (485 metres)
above the level. A notable highlight in the area's arid landscape is this large volcanic rock
structure.
11. Draw a sketch through the Earth’s surface to show the relationship of features H, I and J to
the batholith that likely occurs beneath this location (3 marks)
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Location 3: San Andreas Fault, California
Open the “San Andreas Fault, California” folder and double-click on it to fly there.
12. At points K and L you will notice offset stream beds divided by the San Andreas Fault.
Imagine standing on one side of the fault and looking across to the other side of it. What is
the direction of offset and full name of this type of fault (3 marks)?
You would detect a horizontal offset in the direction of lateral movement if you were standing on
one side of the San Andreas Fault and gazing across to the other. A right-lateral strike-slip fault
is best shown by the San Andreas Fault. In a right-lateral strike-slip fault, horizontal shearing
forces along the fault cause the block across from you to appear to have shifted to the right in
relation to your side.
13. Studies indicate that the offset of Wallace Creek started ~13,000 years ago. Use the ruler
tool to measure the current offset of Wallace Creek (1 mark). What is the average rate of
separation along the San Andreas fault over this period in cm/yr? (1 mark)
2.5 cm/yr
14. Given the separation rate calculated in Q.15, discuss what Southern California will look like
~50 million years in the future (2 marks)
Southern California might experience dramatic changes owing to the ongoing separation along
the San Andreas Fault some 50 million years from now. Islands would eventually arise when the
area broke up into smaller landmasses as some of the land moved northwest with the Pacific
Plate. Over time, these islands would grow in size, changing the landscape and bringing up new
maritime elements. Due to the long-term impacts of plate tectonics, the terrain would be
characterized by a complex archipelago, and Southern California's current familiar shape would
be unrecognizable.
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