Download Field Trip Guide

Oceanography Field Trip
Garrapata Beach
March 8/9, 2014
Introduction
Exploring sediments and rocks of the seafloor is one theme of the on-land field trip. As
we travel from stop to stop imagine yourself traveling around on the seafloor. We’ll be
able to visit many of the seafloor areas we’ve talked about in class, including a mid-ocean
ridge and the deep sea floor of the abyssal plain.
Another theme of the field trip is the coastal processes of dunes and beaches, and
the contrasts between the rocky emergent coastline of Big Sur and the smooth, sandy
coastline of a more stable environment like Marina and Ft Ord.
The last theme of the weekend field trip is the collection of beach profile data.
You will use this field trip guide in an upcoming next Oceanography lab.
Monterey Formation on Olmstead Road.
The most important thing to notice here is the
Monterey Formation Diatomaceous Shale. To the naked
eye, this rock looks like mudstone. But if we had powerful
microscopes, we could see all of the diatoms that comprise
this rock. Since there is very little terrigeneous material in
the rock, we know that it was formed far from continents.
It was probably formed in the deep oceans of the abyssal
plains.
What is the evidence that these sediments were deposited
in the deep sea somewhat removed from continental
influence?
Through
tectonic processes. When
plates or blocks of rocks
converge, the rocks in the
middle deform in such a
way that they get thicker.
Getting thicker means
creating mountains and
mountain ranges. Imagine
continents colliding and
mountain ranges forming.
Mountaineers at the top of
Mt Everest in the
Himalayas have found
fossils of creatures that
lived in the oceans.
What is the evidence that tectonics moved these rocks up to this spot on the hill rather
than the sea level dropping to expose these rocks?
Ft Ord Dunes State Park
Dunes and sandy beach in a
rapidly eroding environment
that is not rapidly emerging.
The dunes here are big and
extend for a few miles inland.
In fact, we will see evidence
of previous episodes of dune
formation.
Photos from 1997
Look at the photographs to
the left. Where is the bus
parked in these photos? Use a
labeled arrow to show the
location of the bus.
What is the evidence of rapid erosion of the seacliff in this area?
Why do we think this area is not rapidly emerging?
What is the evidence that the dune sands are transported by wind?
Monastery Beach A nearby canyon causes deep water to occur very close to shore here.
Also, good views of marine terraces.
Note the deep canyon that
approaches very close to shore at
Monastery Beach.
What is distinctive about the grain size of these beach sands?
What is distinctive about the slope angle of the beach as it reaches the water?
Why might it be like this?
What do the marine terraces look like near this beach?
How were they formed?
Where does this beach get its name?
Hurricane Point Excellent
view of the Big Sur
coastline, one of the worlds
best examples of an
emergent coastline. It just
doesn’t get any better than
this! The rock here is a
marble, which is a
metamorphosed limestone.
Limestone is deposited in
warm shallow seas where
coral and tropical fish make
it nice to snorkel. Then the
limestone gets
metamorphosed into
marble.
What is the difference between a marine terrace and a wave-cut platform?
What is the evidence here for emergence and for erosion along the coastline?
Andrew Molera State
Park We’ll walk to the
mouth of the Big Sur
River here and see the
results of volcanism and
sedimentation at a midocean ridge. Note the
pillow basalts and chert.
We’ll also note wave
refraction as the waves
move in towards the
beach. Can you find any
pink sand? If you can it is composed of garnet that occurs abundantly in rocks found
upstream along the Big Sur River.
What is the evidence that this group of rocks were deposited near a mid-ocean ridge or
on a seamount?
What is wave refraction, and where can you see it here? Can you see it on the image
above?
What is the evidence here that waves push sand along the beach in a process called
longshore drift?
Describe how the interplay between the forces of the ocean waves and the forces of the
water flowing out the Big Sur River shape the beach in this area.
Garrapata Beach Two main things to see here: the submarine fan turbidites and the San
Gregario Fault. The sedimentary rocks here are distal turbidites. That means that they are
deposited by turbidity currents, but far out on the submarine fan.
What is the evidence that the
turbidites here were deposited far
from shore on the continental rise?
Also at Garrapata Beach, we’ll also see the San Gregario Fault. The San Gregario Fault is
part of the San Andreas Fault system and is one of the faults that separate the Pacific
plate from the North American Plate. It is a right-lateral fault, the same kind of fault as
the San Andreas Fault.
Where on the beach is the San Gregario Fault?
What evidence enables you to locate the fault on Garrapata Beach?
Draw and label the SanGregorio Fault in the image below. What evidence enables you to
locate this transform fault?
Garrapata Beach Profile Data
Please record your beach profile data on this page. Bring these sheets to the next
Oceanography lab. Remember to fill in the distance from the benchmark to the sand on
your data sheets. See the next page for photographs of all the benchmarks. Please do your
profile twice, and fill in the data under the A and B columns. Remember to record
negative numbers when going downhill and positive numbers when going uphill (if ever).
Northern
profile
Vertical distance
from benchmark
to sand is station
zero.
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New Northern
profile
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zero.
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Central profile
Stairs Profile
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Southern
profile
Vertical distance
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zero.
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Garappata Beach
For which profile did you collect data (circle one)?
Record the distance from the benchmark to the sand on the table as a negative number.
North
In the
Granite
“New” Northern
In the Granite
Stairs