Name:
Date:
Period:
UW-GEOLOGY 101, FIELD TRIP: TERRANES OF THE SAN JUAN ISLANDS
At each stop, answer questions and make observations about the geology of the area. There will be a
short discussion of the geology at each stop from which you will need to take notes.
STOP 1. ROSARIO BEACH AND ROSARIO
HEADLAND, FIDALGO ISLAND
Use the Rosario Beach and Headland Sketch Map
to locate the sites.
Task 2: Site B, Sedimentary Layers in the Low
Bluffs of the Neck of the Headland
4. Describe the sedimentary deposits.
A. Do you see layering?
Task 1: Site A, Shoreline Processes
1. Use a compass and draw a north arrow
prominently on the map.
2. Make observations about the angle at which
the waves are hitting the beach. Make
observations about how sediment is being
transported on the beach; i.e. are the pebbles
larger at one end of the beach than another,
can you watch pebbles migrating down the
beach in one direction or another? Draw an
arrow showing the direction of beach drift on
your map.
B. Are the deposits well-sorted or poorlysorted?
C. Composition of the clasts (all the same
rock type or different)?
D. Are there fossils in the deposits?
3. While standing on the beach, take an overall
look at Rosario headland and all the land
connected to it. What will eventually happen
to Rosario Headland as shoreline erosion
progresses?
5. What is the origin of these sedimentary
deposits? What evidence supports your
conclusion?
Task 3: Geology and Structure of Rosario
Headland, Sites C, D, E, F.
Please use extreme caution! These rocks are
sharp and the cliffs are steep.
E. What types of marine life do you find in
the tide pools?
6. Site C, Located on the wave-cut platform at
the bottom of the headland.
A. Name the rock.
7. Site D, located upslope from Site C.
A. Name and describe the rock.
B. Describe the rock and draw a sketch with
scale.
B. Rock deformation: Are the layers
horizontal or tilted?
C. Find a distinctive layer and follow it. Is it
folded? Faulted?
8. Site E, located below the cliff (the top of this
rock unit can be viewed from Site D).
C. Rock deformation: Are the layers
horizontal or tilted? Describe the
orientation of strike & dip.
A. Describe the rock (color, possible origin).
If it’s high tide, you might have a more
difficult time reaching the rocks, so do the
best you can.
D. Find a distinctive layer and follow it. Is it
folded? Faulted?
B. Do they appear the same or different as
Site C and D?
9. Site F, the rock that makes up the cliff face to
the south. These rocks can be viewed from
Site E and will have to be viewed from afar.
B. Could it have eroded out of the bedrock
here? If not, how did it get here?
A. Name the rock type. Describe the rocks
and draw a sketch with scale.
11. Summarize the geologic history of Sites C, D,
E, and F. Draw the layers in the order that
they were formed from oldest at the bottom
to youngest at the top. Interpret the history
as seen from the sequence of rock types.
Youngest layer
B. How do these rocks compare with those at
Site E?
Oldest layer
C. Were these rocks erupted on land or
under the sea? Explain.
10. Site G, find the large, rounded boulder on the
south side of the headland.
A. What kind of rock is it?
STOP 2. SUNSET BEACH, WASHINGTON
PARK
C. What is the evidence for a marine origin
(that is, deposition BELOW sea level) of
the glaciomarine drift?
Task 1. Bedrock geology of Washington Park
12. What is the name of the bedrock? Where
could it have originated?
13. How did this rock get to the surface of the
earth?
D. The glaciomarine drift layers are now
ABOVE sea level. Explain how this might
have happened.
14. Describe the minerals in these veinlets (color,
hardness, form).
16. In what direction did the glaciers move? How
can you tell?
Task 2: Glacial Geomorphology (Evidence for
Glaciation)
15. What is the evidence that glaciers moved over
this area?
A. Evidence for erosion by glacial ice?
Task 3: Correlating Outcrops
Use your observations from Task 1 and 2 to
interpret the geologic history of this area.
17. How do the ultramafic rocks seen here
correlate to the rocks seen at Rosario
Headland?
B. Evidence for deposition of material by
glacial ice?
18. In this box, draw a cross-section of the two
rock units we observed.
A. Next to the box, write a few words that
describe the implied events that took
place in order to form the stratigraphic
sequence that we observe.
STOP 4. MOUNT CONSTITUTION & THE
MOUNT CONSTITUTION FORMATION
21. Pending weather, you should have a great
view of Puget Sound and the San Juan
Islands. After you take in the view, look at
the rock you’re walking on. Why are these
outcrops so rounded and smooth?
B. Be sure to include the UNCONFORMITY.
22. Describe and identify the rock type here.
STOP 5. NORTH BEACH & THE NANAIMO
GROUP
25. Describe the rocks on the beach (types,
sorting, roundness).
STOP 3. BURROWS CHANNEL TRAIL,
WASHINGTON PARK
Look for a bedrock outcrop on the south side of
the trail. Fragile rocks!! Please be gentle and do
not harm this beautiful exposure. Preserve it for
future generations of geology students.
19. Describe what you observe in this outcrop.
Include a sense of scale in your description.
26. Where did these rocks come from? How do
you know?
20. How did these features form in this outcrop?
27. Why is Sucia Island shaped the way it is?
Describe the shape and how it was formed?
STOP 6. FERRY TERMINAL & THE MT.
CONSTITUTION FORMATION
30. This is a much better outcrop to examine rock
type than on top of Mt. Constitution itself.
Describe the rock type.
31. Interpret the geologic environment in which
these rocks were deposited.