Virtual Field Trip along Chuckanut Drive and to LarrabeeState Park

• This slide show is a tool to help you sort out what you saw on the field trip. It is in no way a complete replacement for going on the actual field trip, either with the class or by yourself.

• As you go through the slides be sure to have the field trip packet with you. The slides are organized by the field trip “Stop” numbers.

• Your first goal is to formulate specific geologic answers to all the question on the slides and in the field trip packet.

• Your second goal is to use what you saw (data/items) and your answers to the questions to formulate a Relative Age Sequence on your Final Field Trip Worksheet.

• Your third goal is to be prepared for Quiz #2: Post Field Trip Quiz.• Your fourth goal is to use your Relative Age Sequence to write the Critical

Thinking Paper #2

Stop 1- Donovan Avenue BoulderStudents are standing next to part of the original Donovan Boulder, which was about four times as big before it was blown up. How and when was the boulder transported to and deposited at this location?

Close-up view of the boulder. What is the geologic name of this rock?

Stop 2 – Beach at Larrabee State Park

• Exposure of bedrock at the beach. This is the same bedrock that makes up all of ChuckanutMountain. On the left side of the cliff the rock has its fresh color, the dark portion to the right is wet. In the foreground is the gravel portion of the beach deposit.

Stop 2

This is the same exposure of bedrock but viewed looking east. You can get a sense that the layers are tilted to the left.

Close-up view of the bedrock. What is the geologic name of this rock?

Stop 2 - continued

Close up of the gravel portion of the beach deposit at Stop 2. Also, present in the beach deposit is sand (not visible in photo) which has the same color as the bedrock?

Even closer view of the gravel. Was the gravel of the beach deposit derived from the bedrock? If your answer is “no” you have some geologic explaining to do, stay tuned.

Stop 3 – Point at Larrabee State Park

• The point has the same bedrock as Stop 2. Students are standing on steeply tilted layers in the bedrock. The kneeling student is touching an unusually smooth surface that needs an explanation for how it formed.

Stop 3 - continuedClose-up view of the edge of a layer. Notice the pen, it is aligned with what was the original horizontal layer. Also, notice line curving up and away from the pen, these are cross beds. The cross beds contain poorly sorted sediments (not visible but an extremely important fact).

Very close-up view of different cross beds. The faint black lines are two sets of cross beds, the black color is due to the occurrence of black sand grains. What do both of these cross beds indicate about how these sediments were transported and deposited?

Stop 3 - continued

A cliff at Stop 3 reveals a second type of rock in the bedrock.

A close-up view of the second rock type. It is composed of mostly rounded pebble sized grain mix with sand. What is the geologic name of this rock?

Stop 3 - continued

• Close-up view of the “unusually smooth surface” mentioned earlier. This surface has subtle scratch marks that are parallel to each other and orientated in a north-south direction (note the pencil, it is parallel to he scratches). What processes could have created the smooth surface and the “scratch mark”? When did this process occur? Also, you need to translate “scratch mark” into an official geologic term.

Stop 3 - continuedThe same bedrock with the “unusually smooth surface” is on the left and to the right it is buried by a deposit of sediment. The contact between the sediments and the bedrock has a special geologic name, what is that name?

Close-up view of the deposit covering the bedrock. The deposit includes the large boulders in the vegetation. Describe the deposit with range of sediment sizes (sorting) and arrangement (layers or not). How and when were these sediments transported and deposited?

Stop 4 – Chuckanut DriveThis student is checking out the bottom of a nearly vertical layer of siltstone which occurs along with the same bedrock you saw at Stops 2 and 3. The radiating lines are fossil plant impressions. What kind of plant left this impression?

This photo was taken nearby by a WDOT employee while cleaning up a rock slide. It contains the same but more complete plant fossil. What was the sedimentary environment at the time these plants were buried? What do the plant fossils indicate about the climate at the time of deposition?

Stop 5 – Chuckanut Drive…Blanchard Mountain

You are now on Blanchard Mountain which is composed of different bedrock than Chuckanut Mountain. In the field trip handout it is known as the “dark rock”. The cliff of “dark rock” also contains white quartz veins which formed shortly after the dark rock formed.

Close-up view of dark rock. Note the rock is thinly layered with no visible crystals but a shiny surface. What is the geologic name of this rock?

Stop 6 – Cove at the north end of Clayton BeachThe bedrock of Chuckanut Mountain is officially known by geologist as the ChuckanutFormation, which contains many layers of four different rocks. Three of the four are present in this outcrop, plus the orange material is a layer of volcanic ash which was deposited along with the sediments.

Close-up of the three rocks plus volcanic ash layer. What are the names of these three rocks? What do these three rocks indicate about the sedimentary environment for all of these sediments? There were many plant fossils at this Stop as well.

Stop 7 – Sand Bluff at Clayton Beach is a “bluff”

It is a bluff for two reasons; 1) it is a steep landform parallel to the shore and 2) the deposit is a fake, it is a man made deposit.

For the sake of geologic history forget about the fake deposit. However, consider it as a stand-in for a real deposit we do care about and is pictured on the next slide.

Stop 7 - continued

• This photo shows the real deposit which you need to observe in place of the fake deposit. The view is about 1 meter wide and part of a deposit of unconsolidated (not rock) sediments. The whitish items are fossil shells. Describe the deposit with range of sediment sizes (sorting) and arrangement (layers or not). How and when were these sediments transported and deposited? (Hint: look up “glacial drift” in textbook.) This deposit occurs above sea level today. What caused this deposit to be above sea level and when did it get there?