hikers guide geology crater lake

8/15/2019 Hikers Guide Geology Crater Lake

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A Hiker’s Guideto the Geology o

Crater Lake

Mark I Moore


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Notes & Drawings


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Notes & Drawings

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Reference Materials

Books

Bishop, A.C., et Al., Cambridge Guide to Rocks and Fossils. Cambridge University Press, 2001.

Bishop, Ellen Morris, In Search of Ancient Oregon: A Geological and Natural History. Timber

Press Inc., 2003

Bowen, N.L., The Evolution of the Igneous Rocks. Dover Publications Inc., 1956.

Bullard, Fred M., Volcanoes of the Earth. University of Texas Press, 1976.

Busby, Arthur B. III, et Al., The Nature Company Guides: Rocks and Fossils. Time Life Books:Sheena Coupe Publishing, 1996.

Ibid - Volcanoes: In history, in theory, in eruption. University of Texas Press, 1962.

Davis, George H., Reynolds, Stephen J. (Second Edition), Structural Geology of Rocks and

Regions. John Wiley and Sons, Inc, 1996.

Decker, Robert and Barbara, Road Guide to Crater Lake National Park. Double Decker Press,

1988.

Diller, Joseph Silas and Patton, Horace Bushnell, The Geology and Petrography of Crater Lake

National Park. Washington Government Printing Office, 1902.

Dixon, Dougal, The Practical Geologist. Simon & Schuster Inc., 1992.

Drury, S.A., Image Interpretation in Geology. Allen and Unwin, 1987.

Ekman, Leonard C., Scenic Geology of the Pacific Northwest. Binfords & Mort Publishers, 1965.

Erickson, Jon, Plate Tectonics: Unraveling the Mysteries of the Earth. Checkmark Books, 2001.

Fiero, Bill, Geology of the Great Basin: A Natural History. Reno: University of Nevada Press,

1986.

Gulick, Bill, Roadside History of Oregon. Mountain Press Publishing, 2001.Hall, Anthony, Igneous Petrology. Longman Scientific and Technical, 1987.

Harmon, Rick, Crater Lake National Park: A History. Oregon State University Press, 2002.

Jewell, Judy, Oregon. Fodor’s Travel Publications, 1996.

Judd, Ron C., and Nelson, Dan A., Pacific Northwest Hiking: The Complete Guide to More Than

1,000 Hikes in Washington and Oregon; Fourth Edition. Avalon Travel

Publishing, May, 2002.

King, Philip, B., The Evolution of North America., Princeton University Press, 1977.

9

Chapter 1

Igneous Rocks


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This section describes several

types of igneous rocks found within

Crater Lake National Park. An

igneous rock is created when molten

rock inside the earth, or magma,

begins the process of crystallization

caused by cooling. Generally,

anything that flies, oozes or spits out

of a volcano is an igneous rock. I say

generally because anyone who viewed

the film “Joe Versus The Volcano”

knows differently! Back to the good

stuff. . .

Classification of an igneous

rock begins with two main

observations: (1) texture and

(2) composition. The texture of a rock

identifies how fast the rock cooled

and plays a part in identifying some of

the minerals that compose the

specimen. Go ahead and pick up a

rock lying around. If you can see

crystals on the surface the rock has a

phaneritic texture and indicates that

it cooled slowly from its magmatic

state. On the other hand, if you are

unable to see crystals on the rock,

geologists would say that it has a

aphanitic texture and cooled quickly.

Additionally, the composition

of an igneous rock can also be

determined by the overall color of the

specimen—more specifically, the

darkness of color. We rate the darker,

blacker rocks as mafic (primary

composition of magnesium and iron),

the lighter, creamy colored rocks as

felsic (primary composition of feldspar

and silica), and intermediate rocks

which, as the name implies, has an

even blend of felsic and mafic rock

properties.

Classifying

Igneous

Rocks

71

Phantom Ship,45-47

Pinnacles, The,35,42-43,51

Plinian Column,30

Pumice,18,31

Red Cone Springs,56,57

Rhyolite,15,18

Rhyodacite,15,31,42

Ryhodacitic Obsidean,16

Ring of Fire,26

Scoria,17,56

Shield Volcano,65

Sinnott Memorial Overlook,40,41

Specularite,41,59

Subduction Zone,25,26

Cascadia Subduction Zone—27

Sun Notch, 44,45

Silica Dioxide,11Union Peak,28,65

Vesicular,12

Watchman, The,28,45,59

Wizard Island,59-61


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Index

Andesite,13,62

Annie Creek Canyon,53

Aphanitic,10,13

Applegate Peak,45

Ash,19,29

Bacon, Charles R.,31

Basalt,11,12,14,26

Basement Fracture, 27

Camping-

Lost Creek Campground,35

Mazama Campground,35

Castle Crest Wildflower,48-49

Cinder Cone,56,59

Cleetwood Cove,61,66

Crater Lake

Creation of—27

Cristobalite,65

Dacite,14

Dike,45Earth,21

Continental Crust,22-25

Crust,21,23

Inner Core,21,22,23

Mantle,21,22,23

Oceanic Crust,22-25,26

Outer Core,21,22,23

Felsic,10

Fumaroles,51

Garfield Peak,62,63

Geographic Information Systems (GIS),60-61

Godfrey Glen,50

Gabbro,23

Hillman Peak,28,66-67

Intermediate,10

Kerr Notch,45

Llao Rock,62

Mafic,10,11,65

Mount Mazama,27,28

Eruption,27-29,42

Single Vent Phase, 29,30

Ring Vent Phase,29,30

Mount Saint Helens,15,29

Mount Scott,64

Munson Creek,48 Valley,50

Obsidian,19

Ophiolite,25

Orogeny,26

Pacific Crest Trail (PCT), 34,39,65

Phaneritic,10

11

B a s a l t c o m p r i s e s

approximately 90% of all volcanic

rock on earth. It flows very well andlikes to get out and move about the

landscape. This stuff likes traveling

so much that most of the Pacific

Northwest and parts of Idaho is

covered by a type of basalt called flood

basalt.

There are several types of

basalt on and in

photograph above r

of basalt with sevcrystals towards th

rock. You will

variety of different

on basalt. Basalt is

between 45% to 52%

to large quantities

rust over time.

Basalt

The overall content of silica

(Si) and oxygen (O), commonly

referred to as silicon dioxide (SiO2),

contained within an igneous rock

provides more information about itsorigin and possible composition. More

on that in a bit.

learning about so

common igneous ro

the park.


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Another interesting feature of

certain types of basalt are its

vesicular nature. Vesi . . . What did

you say? Oftentimes, gasses and

water vapor get trapped within themagma forming pockets or vesicles.

These vesicles are perfect for the

formation of tons of great crystals.

Can you say agates?

You will not find too much

basalt near the rim of Crater Lake as

most of it was ejected around the baseof the mountain by other small

volcanoes. It is important however to

know and understand how to identify

this type of rock as it is everywhere!

Geologists try to keep things

as simple as possible. So, if you ever

have trouble understanding terms,

break the word down to its root. It’s

usually fairly no-nonsense.

One more thing about

identifying basalt. Have you ever

noticed when objects are placed in the

sun they tend to fade? Rocks are no

different, especially basalt. Take a

look at the pictures below. They are a

prime example of a process calledchemical weathering. This process

affects most rocks but more noticeably

darker, mafic rocks such as basalt.

Notice the extent of color change in these rocks!

Remember that not all rocks are what they appear.

69

The map below shows the many different types of magm

volcanic material that are in the area of Moun

Additionally, the map identifies more than 10 geologic ftheir relation to the various types of volcanic discharges.


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North Entrance Road

South

Entrance

Pinnacles Drive

Rim Drive East

Crater Lake: Moderate and Strenuous Trails

Key

1. The Watchman

2. Cleetwood Cove

3. Mount Scott

4. Garfield Peak

5. Union Peak

Highway 62

2.

5.

4.

1.

3.

13

Andesite is the most abundant

rock at Crater Lake. It is an

intermediate rock, with 53% to 65%

silica and varied content to include

feldspars and others within the

silicate group. The rock’s spotty

appearance is mainly attributed to a

mineral called plagioclase feldspar.

This mineral creates beautiful

crystals seen by the naked eye.

Andesitic magma commonly

erupts from stratovolcanoes as thick

lava flows, some reaching several

kilometers in length. Andesite magma

can also generate strong explosive

eruptions to form volcanic flows,

surges and enormous eruption

columns of magma. Andesitic

magmas erupt a

between 900°C and

is an intermediate i

generally has a gr

basalt which is usua

and without the gre

moderately quick

Whoops, there is

words again.

Andesite’s

from the Andes Mou

South America. Th

primarily found ar

Fire (skip ahead to

really can’t wait) an

lava which hav

mineral content.

Andesite


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Cleetwood Cove

The boat ride available at

Cleetwood Cove affords an excellent

opportunity to view features within

the lake with a fairly unique view.

One geologic feature that attracts

attention during the boat ride is

Hillman Peak as seen here from a

lookout point on the rim.

Around 70,000 y/a a volcanic

vent formed on the flank of Mount

Mazama. These vents typically emit

heavily acidic gasses and other

noxious fumes from the magma

chamber. It acted as a pressure relief

valve for Mount Mazama. When the

top of the mountain collapsed forming

the caldera, it pulled half of the vent

inside the chamber leaving the

innards of the vent exposed. Look

back at the diagram on page 30 for a

refresher on the collapse of Mount

Mazama and the creation of the

caldera. The gasses inside of the vent

oxidized the surrounding rock causing

it to discolor providing us with

the magnificent portrait seen here.

This hike has a fairly extreme

vertical descent so be prepared.

Children are not recommended on

this hike.

15

eruptions from Mount Saint Helens

from 1980 through 1986. Watch out

when identifying dacite. After many

millions of years dacite cones often

break into thin la

head of lettuce.

misidentify this rock

layered type of rock

Rhyolite

The bulk of Crater Lake

National Park’s rhyolite is mixed in

with dacite to form rhyodacite. There

is another one of those geologic terms

again. Break it down into its root and

you come up with rhyolite and dacite.

I guess it could be considered a hybrid

rock!

Rhyolite is the god (or goddess)

of all silicic magmas. It contains 70%

or more silica along

and minerals. If yo

to identify a possib

they are usually l

shades of brown, g

white. Look for

colors in one rock

somewhat layered a

Since rhyolit

contain high quant


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for the stuff closer to the rim of

Crater Lake. If you want to see a nice

chunk of ryhodacitic obsidian, drive

on the north entrance road towards

the lake. Stop at the first turnoutpast Pumice Desert. Great stuff!

Chunks of Ryhodacitic

Obsidian with rock

hammer & crayon for

scale.

Rhyolite (top & bottom).

Notice how the color varies

between rocks

65

Union Peak

This delightful trail utilizes

part of the PCT and then branches off

to the right (traveling southbound) to

the hike up the peak. Although

Union Peak is off the beaten path it is

geologically significant.

The most eye-popping featureof the mountain is its horn shaped

peak. The peak represents a

hardened plug of magma that halted

more liquid rock from escaping the

mountain. The plug is composed of

54% silica which would make it mafic

and very dense. The plug is olderthan Mount Mazama but not more

than one million years of age.

Throughout the years, glaciers

stripped away the looser, less dense

material leaving the plug exposed to

the elements.

Union Peak is an old shield

volcano which further reinforces its

mafic classification. The Hawaiian

Islands are great e

lapping shield volc

mafic magma is very

to travel about t

builds upon itself a

layer until it create

of a shield.The rocks o

the southeastern a

side contain a silica

in very few place

Cristobali te is

equivalent to quart

crystalline componecessary to have

other magnifying d

crystals as they are

meter in diameter

ended, four-sided

Look for them in th

If you didn’t bring y

are out of luck for no

Union Peak

Distance: 2.9mi./4.6km.

Difficulty: Moderate+

Trailhead: 2.8 miles south of highway 62, 42°51.220N 122°1

PCT trailhead.


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Mount Scott

The trail up to Mount Scott is

a real kicker. Bring a plentiful supply

of water and your binoculars. The

views from the fire lookout are

spectacular. With a peak of 8,938

feet, it is the highest point in the

park.

Mount Scott is a 420,000 year

old volcanic cone that rests on the

flank of Mount Mazama. The west

side of the mountain was destroyed

by glaciers. See if you can find any

signs of glacial activity and enjoy the

view.

Mount Scott

Distance: 2.5mi./4km.

Difficulty: Moderate+

Trailhead: East Rim Drive across from Cloudcap overlook

17

I created a quick reference chart to consolidate t

discussed in the last few pages. It is helpful when trying to

the more basic information about these four types of igneous ro

Name Basalt Andesite Dacite

Classification Mafic Intermediate Felsic

Silica content


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Growing up in Southern

Oregon, I have fond memories of

collecting various rock specimens to

see which would float. And after all

those years it still fun to watch.

Many books and other

literature on volcanism (the study of

volcanoes) refer to pumice as frothy

glass. It is the compositional

equivalent of rhyolite except that

this rock contained huge amounts of

gas when it was ejected from a

volcano. Since pumice has an

extremely high silica content

Pumice cools so quickly that crystals

do not have time to organize

themselves. Therefore, pumice must

be. . . aphanitic or phaneritic?

Pumice

Notice the great colors in this pumice sample—a crayon used for scale.

Remember that not all pumice will be high and dry so look for varying colors.

63

Garfield Peak


Difficulty: Moderate

Trailhead: Far east end of Rim Village on the other side of

U-shaped glacial

valley

Llao Rock

with dotted

lines rep-

resenting the

former glacial

valley. (top &bottom)


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Chapter 2

Our Dynamic Earth

61

represent post-caldera volcanic

activity or small eruptions of magma

after the initial eruption of Mount

Mazama.

If you choose to hike the two

trails on Wizard Island, be prepared

to hike up a fairly steep incline. The

slopes of this cinder cone have a nasty

35° angle with a spi

1.6 miles. Unfort

way to access th

boatrides available

which are quite exway, Wizard Islan

representation of h

the most beautiful s

The Watchman


Difficulty: Moderate

Trailhead: West Rim Drive, 42°56.375N 122°10.350W, larg

Offers lookout to Wizard Island and other signi


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58

North Entrance Road

South

Entrance

Pinnacles Drive

Rim Drive East

Crater Lake: Easy Trails

Key

1. Sinnott Memorial Overlook

2. The Pinnacles

3. Sun Notch

4. Castle Crest Wildflower

5. Godfrey Glen

6. Annie Creek Canyon

7. Red Cone Springs

Mazama

Campground

Highway

62

4.

3.

2.

1.

5.

6.

7.

23

within the earth, there are many

structural changes that occur within

this layer. The mantle has a

generally uniform composition

throughout. However, increasingpressure from the strata above

changes the crystalline structure of

the minerals.

The last and most familiar

layer of the earth is the crust. Only

0.7% of the earth’s mass is found

here. There are two types of crust;the continental crust and the

oceanic crust. Geologists and

others know more about these two

layers because they are easier to

access.

The continental crust is the

lightest portion of the earth and themost complex. On average, it is about

21 miles thick but varies throughout

the continents. It holds a variety of

different types of rocks to include

igneous, sedimentary (break it down),

and metamorphic. Overall, the

continental crust is granitic.

Granite is

equivalent to rhyo

contains quartz, mi

All of these minera

in weight in comparheavier compositio

basalt. If you wa

about any of t

minerals, go online

bookstore and pick

minerals fieldguide

worth the $15 or $20

Because hu

ability to measur

(waves produced by

have observed the

sea-floor with d

platforms and subm

that the upper port

crust is composed

lower portion is com

Gabbro is m

than its counterp

contains essenti

minerals. Howe

phaneritic. For a r

try page11.

Inner Core Iron/Nickel (10%-20% Nickel)

Outer Core Iron with sulphur and SiO2, nickel and pota

Mantle Peridotite

Continental Crust Basalt (upper), Gabbro (lower)

Oceanic Crust Granite or GranoDiorite

Composition


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26

Mountain Building

The Ring of Fire? No, this has

nothing to do with a group of hobbits

or a magic ring. The Ring of Fire is a

term used to describe the perimeter of

the Pacific Plate which extends fromthe west coast of the United States,

north through the Aleutian Islands,

west to Japan and through New

Zealand. This perimeter outlines the

ring of the Pacific Plate. Historically,

70% of all active volcanoes occur onthis belt.

The process of orogeny, or

mountain building, is still not fullyunderstood; however, it is currently

known that plate tectonics is directly

responsible for the creation of

mountains. Here is the general idea:

The oceanic crust is subducted

(remember, the heavier crust is forced

under the lighter crust) along with

some of the sediments lying on the

bottom of the seafloor. Thesesediments, which are under extreme

heat and pressure from subduction,

melt and mixes with the partially

liquefied oceanic crust. The basaltic

crust of the ocean mixed with the

higher silica content of the

continental crust. The mix of basalt

55

Annie Creek Spring

Annie Creek Spring does not

have a hugely defined trail leading to

the source however it is significant in

this context. As you pass Mazama

Campground traveling north on the

south entrance road, park on the left

hand side before the bridge. When

you arrive at the

pristine nature of th

now looking at the

source for Rim Vill

Village. Please, try

You are drinking th


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volcano. The image below, painted

by Paul Rockwood, represents the

probable appearance of Mount

Mazama prior to the formation of

Crater Lake.

As demonstrated by this

painting, Mount Mazama had a

number of smaller peaks around the

perimeter called cinder cones. These

volcanoes and other geologic

phenomenon acted as vents for the

great mass of gasses and magma that

escaped from the magma chamber

lying below the mountain. Some of

the more well known vents and lava

flows include Hillman Peak, The

Watchman, Union Peak, Cleetwood

Flow, and Williams Crater (a.k.a. For-

gotten Crater) which is a cinder cone.

We’ll talk more about cinder cones,

parasitic cones, and vents of Mount

Mazama when we get into the trails.

Throughout the formation of

Mount Mazama, there were several

53

Annie Creek Canyon

The Annie Creek Trail is a

beautiful example of how nature has

sculpted the landscape. As you

descend the narrow and windy trail,

take notice of the layering affect

visible on the fumaroles caused by the

varying compositional eruptions. Also, take the time to examine the

diversity of flora, fauna, and geology

on this trail. Before crossing your

first log bridge in the canyon, you will

probably have a few questions about

the odd-shaped walls.

The series of graphics on theright demonstrates the 4 main

processes which shaped the walls of

Annie Creek le ad ing to such

spectacular views. After the eruption

7,700 y/a, Annie Creek started feeding

water into the canyon again eroding

the loose pumice and ash. The

pumice that had been heated and

cemented together by escaping gasses

is more resistant to erosion and was

therefore left behind creating the

canyon walls as we see them today.

As the trail winds through

Annie Creek Canyon stop and enjoy

Streams created

a V-cut canyon.

Once again,

water cuts

through the

valley creating a

V-cut.

Glaciation

occurred on the

flanks of Mount

Mazama

creating U-cut

valleys

The eruption of

Mount Mazama

filled in the

glacial valley

with pumice,

ash and other

pyroclastic

material.


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Godfrey Glen

Distance: 1mi./1.6km., loop trail

Difficulty: Easy

Trailhead:

South entrance road headed towards, approximately 0.5 mile

from Mazama Camprground, pullout road on the right side of the

road.

29

main periods of increased activity.

These and other events are outlined

in the chart above. Let’s get moving

to the eruption of Mount Mazama

that created the majestic Crater

Lake.

Around 7,700 y/a, Mount

Mazama erupted w

explosive power tha

Mount Saint Helens

have been one hell

eruption covered m

square miles with called tephra, and

cubic miles of magm

mainly covered the

portions of North

pyroclastic material

Mazama is covered

thick while 70 milefoot thick. There

stages of eruptions

form Crater Lake

include the (1) sing

(2) ring vent phase.

During the si

Summary of Events Leading to the

Creation of Crater Lake

~40 million y/a Beginning formation of the Cascade Moun

~2 million y/a Formation of Mount Mazama's magma ch

beginning of the mountain's formation

~420,000 y/a First major eruption~350,000 y/a Increased period of mountain building

~200,000 y/a Southern Mazama, Dutton Cliff area form

~100,000 y/a Dark Andesite built cinder cones on south

~75,000 y/a Andesite flows built Hillman Peak and roc

Cloudcap Bay. Dacite & rhyodacite flows b

~25,000-30,000 y/a Primarily rhyodacite flows which erupted

~22,000-12,000 y/a More andesite flows, creation of The Watc

~75,000-6,900 y/a Creation of upper parts of Mount Mazama~7,700 y/a Cataclysmic eruption forming Crater Lake


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50

Godfrey Glen

The mild 1-mile loop trail at

Godfrey Glen represents another

example of Mount Mazama’s

awesome power during its last

eruption. If you remember on page

29, the prevailing winds during the

time of the eruption were headed

north and northeast, carrying scores

of ash and pumice to the affected

areas. The Lower Munson Valley at

Godfrey Glen was blanketed with

approximately 250 feet of ash and

dacitic pumice. When the mountain

had expelled its sources of dacitic

31

rocks that were once solid became

obliterated and eruptions of pumice

and other types of frothy glass were

expelled; approximately 3.5 cubic

miles of pumice are thought to becreated during the second phase of

eruption.

Based on research by Charles

R. Bacon and others, it is suggested

that Mount Mazama had a stratified

or divided magma chamber. All of the

lava from the first

silica rhyodacite.

second or ring vent

began as rhyodacite

basalt-andesite. Vout the Cascade Mo

the rest of the wo

erupt the same type

variety, which mak

Mount Mazama an

wonderful phenome

.

I hope that you got all of that.

That was a great deal of information

to take in. There will be plenty of

time for review later. For now, let’s

start talking about

need to know befor

Crater Lake Nation


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32

Chapter 3

Things to Know Before you

Go Hiking in Crater Lake

National Park

49

Castle Crest Wildflower Trail

Distance: 0.4mi./0.25km., loop trail

Difficulty: Easy

Trailhead: Less than one-quarter mile east on East Rim Dr

parking area with the trail visible from the road

signage. Alternative spur trail beginning at Par


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34

Fees & Other Costs

The fee schedule is fairly

reasonable considering you are

visiting one of the most amazing

spectacles in the United States. If

you are not hiking through the Pacific

Crest Trail (PCT) and decide to drive

around the park, it will cost you $10.

For those cyclists who are a little

more daring, it will cost you $5. The

entrance station personnel provide a

park map and information during

summer hours.

Parking is free at Rim Village

and other lookout spots around the

park. If you are a PCT hiker and

camping in the park, you will need a

free backcountry camping permit.

You can obtain a permit at both park

visitor centers. The purpose of these

permits is to attain a tally of hikers

spending the night in the wilderness.

It’s for your safety as well.

The boat ride around the lake

costs $23.50 for adults and $13 for

children and leaves every hour on the

hour from 10a.m. to 4p.m.

State of Oregon, Crater

Lake quarter.

47

Sun Notch


Difficulty: Easy

Trailhead: East Rim Drive, between Dutton and Kerr Ridg

(42°54.002N 122°05.730W), large pullout with c

trailhead sign.

Phantom Ship


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36

A quick reminder about hiking in the park. Remember that you are

probably walking at a higher elevation than at home. The higher you go, the

less oxygen there is to breathe. Know your limits, take your time and enjoy the

scenery. Here is a list of things that will enhance your hiking as well as your

understanding of fundamental geological knowledge.

□ 10x hand lens or magnifying glass for looking atcrystals in the rocks

□ Rocks and Minerals handbook

□ Small backpack or Camelback for carrying water, food

or spare clothing

□ GPS (not required but helpful)

□ Compass (if you forget to bring batteries for your GPS)

□ Pencil and paper if you choose to draw or write down

your observations

□ If you must, bring your cellular telephone . . .

□ Rain gear is a good idea

□ Camera and film or extra batteries for your digital

□ Bug juice

□ Park map (provided at the park entrance stations)

□ Binoculars

Items to Bring With You

45

the trees and into the meadow, you

may be wondering, “What is that

beautiful layered peak to the left of

me?” It is called Applegate Peak. Ifyou have binoculars take a closer look

at the varying multi-color layers of

igneous material. Each layer

represents a different flow of magma

that contained its own distinct

mineral content. It truly is

magnificent.

Once you arrive at the part of

the trail that parallels the rim of

Crater Lake you will notice several

prominent features. The beautiful

island to your left is called Wizard

Island. It has a story of its own which

we will discuss when hiking The

Watchman. Other

lake and off to the

water’s edge. The

called Phantom Shclosest view of Phan

are going to obtain

those quality pictu

time that you smac

bringing the camera

Phant

remnants of a dikaround 400,000 yea

dike? Think back

when we were ta

formation of Moun

magma rises from t

the earth, it fills an

the crust. Instea

Kerr Notch Sun No


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44

Sun notch

This short jaunt through a

grassy meadow should prove utterly

delightful during any time of the year.

As you begin your hike, just try to

imagine that several million years

ago there used to be a glacier right

where you are standing.How do geologist know? There

are several indications that geologists

use to map the existence and path of

glaciers. When glaciers retreat down

mountain tops or other topographical

features they carve out massive

U-shaped glacial valleys, versus a

V-shaped valley carved by water.

More on that later. Two of these

large glacial valleys exist on the rim

of Crater Lake: (1) Kerr Notch and (2)Sun Notch. The photograph on the

opposite page demonstrates this

U-shaped phenomenon.

As you make your way through

37

Things you Are Not Supposed

Because Crater Lake National Park represents nature at its

and outdoor aficionados wish to preserve nature’s legacy. Alth

to be told what to do, I submit this list as a guideline for your

accordingly. Here are my suggestions:

□

Stay on the trails—it would be nice to leave naturits thing without your size 9

□ Leave rocks and native plants where they belong—

nature

□ Keep our water clean. Place your junk somewher

Pack it out!

□ Pets should stay at home

□ Bicycles should stay on the pavement or in design

areas

□ If you must smoke, do it in your car. I don’t want t

smell you either!

□ The animals in the park have done just fine witho

your food inputs. Let’s leave it that way.


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38

Chapter 4

Trails

43

The Pinnacles


Difficulty: Easy

Trailhead: East Rim Drive, dead end at The Pinnacles Road

through Kerr Valley, the trail begins at the turn


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42

The Pinnacles

During Mount Mazama’s most

recent eruption around 7,700 y/a, red-

hot avalanches of ash, pumice and

gasses came rumbling down the

mountain. The first of these

avalanches corresponded with the

single vent phase of the eruption,

spewing out rhyodacite and other high

silica materials. The following

avalanches from the ring-vent phase

consisted of grey andesitic scoria.

Temperatures of these avalanches

were around 750° Fahrenheit when

they landed in the canyon.

Throughout the many years it

took for the avalanches to cool, gasses

within the avalanches sought a way

out of the overlying material. These

hot gasses escaped upwards forming

tube-like caverns or gas vents called

fumaroles. As the gasses rose, theywelded the scoria and other

pyroclastic material together forming

the tube-like structures in the

pictures on this page and the

following page.

The obvious change of color of

these tube-like structures from the

bottom to the top is caused by the

change of output by Mount Mazama

f r o m r y h o l i t i c m a g m a a n d

particulates to andesitic.

39

Welcome to the Trails section

of the book. The trails are first

organized by their difficulty and then

their distances. There are a few trails

which require travel on the PCT

before arrival at the trailhead. Those

distances are incl

dialogue of the tra

include a map at

section separated

Enjoy!

Trail Name

Length (1-way unless

loop) Diffic

Sinnott Memorial Overlook ~75 feet Easy

The Pinnacles ~0.25mi/0.4km Easy

Sun Notch 0.25mi./0.4km. Easy

Castle Crest Wildflower Trail 0.4mi./0.6km Easy

Wildflower spur 0.4mi./0.6km Easy

Godfrey Glen 1mi./1.6km Easy

Annie Creek Canyon 1.7mi./2.7km Easy+

Red Cone Springs 4.2mi./6.7km Easy

The Watchman 0.8mi./1.1km Modera

Garfield Peak 1.7mi./2.7km Modera

Mount Scott 2.5mi./4km. Modera

Union Peak 2.9mi./4.6km Modera

Cleetwood Cove 1.1mi/1.8km Strenu

The “+ “ symbol indicates that parts of the trail have incr

However, they do not warrant a higher difficulty rating.


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hikers guide geology crater lake

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