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ESS 305
Mt. Rainier National Park
Spring 2015
31 May
We will examine the southern traverse of Mount Rainier National Park via the Paradise and Stevens
Canyon roads. Remember, this is a national park. There must be NO collecting, hammering, digging,
picking up or disturbing of anything, by law.
Drive south on I-5 to Exit 127 (Highway 512). Set odometer to zero at offramp. Drive east on 512
for 1.9 miles, then turn right onto Highway 7-- offramp followed by right turn at stoplight.
At mile 30.5 and 32.0, stop to view La Grande Dam and Alder Dam, parts of the Nisqually Project.
At mile 38.8, turn left onto Highway 706 East and proceed to the park entrance at mile 53.0. Continue to
mile 56.3, Kautz Creek. Stop on the far side of the bridge. This stop has restrooms.
Stop 1. Kautz Creek (elevation 2378 ft)
Point Success (14153 feet) on Mt. Rainier, with part of the Sunset Amphitheater visible. The many layers
of lava flows and pyroclastic deposits that make up Rainier can be easily seen. Success Cleaver and
Glacier in the middle left, Nisqually Glacier on the right. Puyallup Cleaver on the left skyline, Gibraltar
Rock on the right skyline. The wooded hill to the left foreground is Tumtum Peak (4678 ft), made of NE
dipping Ohanapecosh Formation. Rampart Ridge in the right foreground, not easily seen.
Kautz Creek valley has experienced at least four recent glacial outburst floods (jökulhlaups), caused
when water is temporarily dammed inside the passageways under a glacier. The last big flood took place
on 2-3 October 1947, wiping out the old bridge and roadway, and depositing up to 20-30 feet of sand and
gravel with boulders up to 6 feet across. This deposit knocked down many trees but some remained
standing (the silver snags). The flat bouldery surface covered with young trees is the top of this 1947
deposit.
The 1947 glacial outburst flood, which came after several heavy rains, traveled 6.5 miles down the
mountain and into the Nisqually River. The sizes of these floods depend upon how much water is being
temporarily trapped underneath and inside the glacier. Smaller outbursts in the Kautz valley have taken
place in 1961, 1985 and 1986.
How might we use both the dead and the living trees to determine when the lahar occurred? How tall
are the oldest trees? If we cored the oldest trees, and counted the rings, would there be 68 rings? Why or
why not?
Ignore the live trees for the moment. Could we use the silver snags to determine the date (1947)
when they were buried and killed? If so, how would that work, and if not, why wouldn't it work?
View from the bridge of the eroded bank downstream. Is there an older set of buried trees, older than
the 1947 set, exposed in the bank? Make a sketch of the bank exposure.
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Many of the features on today's trip are tied to glacial activity. Mt. Rainier supports the largest single
glacial system in the contiguous U.S.; its glaciers contain more ice than is found in all the other High
Cascades volcanoes combined.
Continue to mile 64.7. Park on the near side of the bridge.
Stop 2. Nisqually River Bridge (el. ≈3800 ft)
Not much of Rainier is visible from this area. Glacier Vista above Paradise is often marked by
tourists, and hikers slogging up the Muir snowfield are silhouetted against the horizon. Towards the south,
Eagle Peak (5958) and Wahpenayo Peak (6231) rise up behind Ricksecker Point; the cliffs are made from
Rainier lava flows, and show columnar jointing.
The big attraction here is the history of the Nisqually Glacier's advance and retreat. This glacier is
the sixth largest on Rainier, is two square miles in area, and contains about 8 billion cubic feet of ice.
During the "Little Ice Age" the Nisqually advanced 750 feet down past the present bridge, then began
shrinking. The terminus was at the present bridge in 1857, at the old bridge by 1870, and continued to
retreat until 1952, ending almost 5000 feet up from the present bridge. The glacier re-advanced 1000 feet
until 1988, and has not done much since. The present terminus and snout are not visible, hidden around
the corner.
During the retreat of the Nisqually, the glacier often stood still for a few years, and built up
moraines: ridges of angular rubble. Lateral moraines formed on both sides of the glacier, terminal
moraines formed at the end of the glacier. These moraines are now covered with trees and vegetation, but
can still be recognized; the trees can be dated using tree ring counting, and the age of the moraines
determined precisely. There are three sets of moraines preserved around the two bridges. The 1840
moraine is across the road from the parking lot; the 1857 moraine (very subdued) is half way to the old
bridge; and the 1870 moraine is near the old bridge.
We'll walk onto the 1840 moraine; what is the morainal material like? Describe the size of particles,
angularity of particles, composition of particles, etc.
Divide into teams of two and estimate the circumference, in feet, of four or five of the oldest conifers
growing on or near the 1840 moraine. Calculate the average growth rate in feet per year. Douglas fir
from the Nisqually entrance to the park grow at a rate of 1 foot in circumference every 5 years. Give two
reasons for the difference in rates.
Glacial outburst floods have also affected the Nisqually River. The last big flood was in 1955,
augmented by landslides from lateral moraines. The flood took out the old bridge (3908 ft), and left a very
extensive and thick deposit in the valley. This deposit is mostly covered with red alder (also known as
slide alder), except where the Nisqually River floods every spring.
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Turn right at the fork at mile 66.0. Park at the lookout at mile 66.2.
Stop 3. Ricksecker Point (4212 ft)
Pt. Success (14153 ft) on Rainier, with the Puyallup Cleaver on the left skyline, St. Andrews Rock at
11562 ft. Gibraltar Rock and Camp Muir visible on the right. The Nisqually Glacier and Kautz Glacier
both prominent.
To the NW, a series of glacial horns. From right to left: Pyramid (6937 ft), Copper (6306 ft), Iron
(6283 ft) and way to the left Satulick (5577 ft). A large fault separates Satulick and Iron, parallel to the
creek called Devil's Dream. Satulick is made of 30 million year old Ohanapecosh Formation, while IronCopper-Pyramid are made of 25 million year old Stevens Ridge Formation. The fault has dropped the
younger, right side down. Rampart Ridge, made of Rainier lava flows with columnar jointing, is in the
foreground.
To the S, another series of horns. From right to left: Eagle (5958 ft) with Chutla and Wahpenayo
(6231 ft) in the background; Lane (6000 ft) and perhaps Pinnacle (6562 ft) to the left. The upper part of
Eagle and Lane are made of 25 million year old Stevens Ridge Formation, while the lower part of Eagle
and Lane and most of Pinnacle are made of 17 million year old intrusive Tatoosh Pluton. You are looking
at the roof of the originally underground Tatoosh magma pool.
The ridge which ends in Ricksecker Point is made of Rainier andesite. This andesite is gray, fine
grained, and somewhat massive in appearance. This lava flow is actually an old volcanic flow, one of the
early intracanyon lava flows, probably around 1 million years old or less. These lava flows filled up
canyons that had been carved in the countryside by glaciers and/or rivers. You're looking at one of the
upper lava flows in a very thick sequence of canyon filling lava flows. Then new valleys were carved, but
in different places than the original valley; to the left, the Nisqually valley and to the right, the Paradise
valley. So now the original canyon filling lava flow forms a ridge. This bit of serendipity is called
topographic inversion.
At Ricksecker Point itself, the andesitic lava flow is capped with glacial moraine. This glacial
deposit is about 15,000 years old and formed during the last great ice age when all the glaciers around
Rainier were much larger than today. Glaciers must have completely filled the Nisqually and Paradise
valleys; valley glaciers must have been at least 1000 feet thick here. The deposit is only a few feet thick;
the deposit was probably thicker, but has been eroded away.
Continue to mile 68.6. Restrooms at this stop.
Stop 4. Narada Falls (4572 ft).
The Paradise River used to drain from Paradise Glacier, but the glacier has shrunk so much in the last
100 years that all the water from the glacier goes down Stevens Canyon to the east. Paradise Glacier water
used to flow into Puget Sound; now it flows into the Columbia River. The Paradise River no longer is
glacially fed; it now gets its water from snowmelt and groundwater.
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We will walk down the trail to view the geology. What kind of igneous rock do we see behind the
falls? What kind of igneous feature does this rock exhibit? Sketch this feature. What does this igneous
feature tell us about the formation of this igneous rock?
On our side, and off to the right, partially coated in green slime, what rock can be seen below? What is the
name of this rock and how old is it?
Consider what was said about “topographic inversion” at the last stop. How will this eventually apply to
this location? When this andesite erupted, it filled a steep valley that had been carved into the Tatoosh
granodiorite. Now the andesite is one of the more durable rocks present.
Turn right at the fork at mile 69.5. Possible brief stop at 70.0-- view of falls and columns. Continue
to mile 70.8.
Stop 5. Reflection Lakes (4561 ft)
Rainier (Columbia Crest) shows Success Cleaver on the left skyline, Gibraltar Rock and Cathedral
Rocks on the right skyline, with Little Tahoma (11117 ft) poking up. From right to left, the Ingraham,
Cowlitz, Nisqually and Wilson Glaciers dominate. Camp Muir above Anvil Rock is visible. Mazama
Ridge leading down from Paradise is in the foreground.
To the S, the Tatoosh Range of peaks. Left to right: hard to see Foss (6500 ft), blocky Castle (6500
ft) and pointy Pinnacle (6560 ft). All of these peaks are capped with roof pendants of 25 million year old
Stevens Ridge Formation; the rest of these peaks are made of 17 million year old Tatoosh granodiorite.
Roof pendants are bits of the original roof of older rocks above the Tatoosh magma chamber. The
granodiorite can be seen across the road and in the wall blocks.
Reflection Lakes formed in shallow depressions on the surface of the Paradise Park lahar. The
lahar is a thin deposit throughout much of the park, but here it's a bit thicker, and therefore makes its own
topography: constructional topography. There are small hummocks in this area as well, probably cored
by large boulders of volcanic rock. The lahar is about 5500 years old, was started somewhere on Rainier
above Paradise, perhaps in the Camp Muir area, and according to some authors, was "catastrophically
ejected."
This area is a major drainage divide. Big Reflection Lake drains to the west, into the Nisqually
River and Puget Sound. Louise Lake drains to the east, into the Cowlitz River and the Columbia.
Continue to mile 75.2. Stop in the large (third?) pullout, just past the interpretive sign.
Stop 6. Tatoosh Pluton (~ 3500 ft)
Large roadcuts through Tatoosh granodiorite and granite, approximately 17 Ma old (formed
approximately the same time as the beginning of the Columbia River basalts). In what plate tectonic
setting did these rocks form?
Continue to mile 78.4. Stop just past the tunnel and bridge. Restrooms at this stop.
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Stop 7. Box Canyon (≈3000 ft)
Nice view of Mt. Adams (12,276 ft) forty miles away.
The rocks around Box Canyon are mostly 20 million year old Fifes Peak diabase. Diabase is a dark
igneous rock with intermediate sized crystals or minerals; it formed underground, but not very deep. It's
almost all dikes at this locality, and only a tiny bit of older country rock here and there. This is a dike
swarm, hundreds of individual dikes, each from 1-10 meters thick. These diabase dikes were most likely
feeder tubes for basalt flows on the surface; those basalt flows are now eroded away, and we're down at a
deeper level, in the originally underground plumbing. In the road cut, we can see the dark green-gray,
medium grained diabase with large dark crystals of pyroxene. The dikes are cut by a few quartz veins
(veins are cracks that are filled with hydrothermal minerals, not magma). There are also several fractures
that are coated with black shiny semi-metallic to sometimes rusty hematite. The metallic version of
hematite is called specularite.
Above the NW tunnel portal, you can see a subhorizontal stripe. What rock makes up this stripe?
What formation does it belong to? How old is this stripe rock?
The "Muddy Fork" of the Cowlitz River has carved a serpentine or meandering channel into solid
bedrock that is 200 feet deep at its maximum. This type of channel is said to be incised. The Cowlitz,
Ingraham and Whitman Glaciers feed the Muddy Fork, which eventually drains into the Columbia River
near Vancouver.
The Cowlitz Glacier, far up on Rainier, once extended down this valley. We can find many glacial
features here, including a nice roche moutonée (sheep rock). Roches moutonées are carved out of solid
rock. Their uphill side is polished and striated, with a shallow sloping surface, while the downhill side is
steep, fractured and rough. The downhill side, the face of the sheep, has been plucked, by water
penetrating cracks, freezing to the glacier and then ripping away at the downslope side. Which way do
these face (what was the direction of ice movement)?
The rocks in Box Canyon were glacially polished, producing rather smooth surfaces. Boulders
frozen into the bottom of the Cowlitz Glacier ground down and polished the bedrock. Those same
boulders also produced glacial striations, long thin scratches in the polished surface. Glacial striations are
very useful for telling the direction of movement of ancient glaciers. Are there one or two sets of
striations? Which way/ways do these striations point? Make a sketch. Show the north arrow.
Continue to mile 83.0. Stop near the far end of the long pullout.
Stop 8. Backbone Ridge (≈3500 ft)
This excellent roadcut exposes the Stevens Ridge Formation, which is about 25 million years old.
The Stevens Ridge Formation is about 500-1000 feet thick in this area; we are looking at the lower portion
of the formation, near its base.
What are the sizes of particles that make up this rock? Are the particles rounded, subrounded,
subangular or angular? Therefore what is the general name of this rock? Make a quick sketch.
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Examine the dominant fragment in the Stevens Ridge Formation. The fragments are usually green in
color because the Stevens Ridge Formation has been lightly cooked. Are the fragments mafic, intermediate
or felsic? Are the fragments coarse grained, porphyritic (two different mineral sizes) or fine grained? Are
the fragments volcanic or plutonic? What is the rock name for this fragment?
There are two vertical features running through the Stevens Ridge rocks. The large one is about 3
meters wide; the thin one is about 1 meter wide. Make a sketch of the field relationships.
Examine the rocks that make up the features: mafic, intermediate, felsic? Fine grained, medium
grained, coarse grained? What rock type (name)?
What are these features called (geologic term)? Are these younger or older than the Stevens Ridge
rocks? Which formation do these belong to? How old are these?
Examine the big feature carefully. What is the difference in mineral size between the rock in the
middle and the same rock at the edge? Explain this difference.
Proceed to mile 89.0, turn left onto Highway 123. At 100.2, left onto Highway 410 West. Rest stop at
mile 113.5, Camp Sheppard Trailhead.
At mile 142.2, right turn on Griffen Avenue to Highway 169 North. At 142.8, right turn on Porter
Street to Hwy 169.
Optional stop, daylight permitting: At 149.0, left onto Green Valley Road to Flaming Geyser State
Park, left into park at mile 157.3. Park at the far end. Backtrack to Hwy 169 at mile 157.3.
At mile 176.8, take onramp to 405 North. At 183.8, exit to I-90 West. Return to campus.