Oceanography Field Trip
March 12, 2011
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 tectonics moved these rocks up
to this spot on the hill rather than the sea level dropping
to expose these rocks?
How did the rocks
move from the
seafloor to the North
American continent?
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.
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 for more than one episode of dune formation?
What is the evidence that the dune sands are transported by wind?
Pt Pinos
How does this coastal
environment differ from
the Marina-Ft Ord area?
What is the evidence of erosion here?
Do you think it is eroding as fast as the Marina- Ft Ord area?
What do you think causes any difference in erosion rate that you might have observed?
What are the characteristics of the sand here?
How does it compare to the bedrock?
Asilomar Beach
How does the sand here at
Asilomar Beach compare
with the sand at Pt Pinos?
What are the similarities and differences between this section of the coast and Pt Pinos?
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 all 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
mid-ocean 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?
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. Remember these rocks
and compare their grain size to the
rocks that we’ll see (or have seen) at
Pt Lobos.
What is the evidence that the
turbidites here were deposited far
from shore on the continental slope?
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 fault that separates the Pacific
plate from the North American Plate. It is the same kind of fault as the San Andreas
Fault.
What kind of fault is the San Gregario Fault?
How were you able to locate the fault on Garrapata Beach? Where is it?
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, in cm.__
A
B
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New Northern
profile
Vertical distance
from benchmark
to sand, in cm.__
A
B
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Central profile
Stairs Profile
Vertical distance
from benchmark
to sand, in cm.__
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B
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Vertical distance
from benchmark
to sand, in cm.__
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B
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Southern
profile
Vertical distance
from benchmark
to sand, in cm.__
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B
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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
Central
In the
Granite
South
Of the
Stairs
“New” Northern
In the Granite
Stairs