Copyright
Ralph S. (Ralph Stockman) Tarr.

A laboratory manual for physical and commercial geography online

. (page 10 of 16)
Online LibraryRalph S. (Ralph Stockman) TarrA laboratory manual for physical and commercial geography → online text (page 10 of 16)
Font size
QR-code for this ebook


of vertical cliffs and gentler talus slopes in this inner gorge?

What is the nature of the river's flow here, as shown by the conventional

sign ?



Human How many houses are mapped on this area ? What two

occupation.

factors account for this very sparse settlement?



Why is a railroad built to the Grand Canyon ?



Why is this canyon an even greater barrier to travel than a high mountain range ?



Write a short paragraph telling what you would expect to see if you were standing at
Yavapai Point and looking out over, and down into, the Grand Canyon.



199



#



Materials.



Purpose.



Introduc-
tory.



Location
of the
Yosemite
Valley.



XLVII. — THE YOSEMITE VALLEY

For Each Student. — The contour map of the United States. The Yosemite (Cal.) quadrangle.
Map of the Yosemite Valley, California.

To gain an appreciation of the setting, scenic magnificence, and topographic relations of the
Yosemite Valley.

The four preeminent scenic resources of the United States are Niagara Falls, the Grand
Canyon of the Colorado, the Yellowstone National Park, and the Yosemite Valley. Three of
these, and the fourth in part, owe their origin and interest to the results of the erosive work of
water, active either as a running stream or in the form of glacial ice. The features of the
Yosemite Valley are the resultant of both ice and water work on a jointed, granite rock. During
the Glacial Period huge glaciers radiated from the higher summits of the Yosemite region,
and, moving downward toward the lowlands, scoured out and differentially eroded their valley
channels, leaving the smaller valleys hanging at their mouths, far above the floor of the main
valleys. As a result of this differential glacial erosion, waterfalls were born when the valleys
were eventually freed of ice, so that the streams could again flow.

Locate the position of the Yosemite sheet on your contour map of the United States, and
outline its area with ink. Letter in the name of the sheet.

As indicated by the contours on the United States map, why is the Yosemite Valley said

to be in the " High Sierras"?



Topo-
graphic
relations.



What is the approximate general elevation above sea level of

the summits in the Yosemite region as shown on the Yosemite quadrangle ?

Of the valley bottoms? Explain the absence of railroads

in this region.

In what respect does the Yosemite Valley differ markedly from other valleys in the region ?



What other valley has similar features on a lesser scale ?



What distinct difference in the valley form of the Hetch Hetchy Valley and

the Grand Canyon of the Tuolumne (both of the Tuolumne River) do you note ?



201



Which of these forms is most characteristic of glacial erosion? -.

Is the form of the Yosemite Valley typical of glacial or stream erosion ?

Examine the map of Yosemite Valley. What particularly striking topographic forms are
indicated by the many areas of crowded contour lines?

How high is the cliff of El Capitan? Describe the

Half Dome as to height above base, shape, and steepness of sides.



What are joint planes?

(Text-book, p. 38.)



How would the presence of such joint planes in massive granite rock

aid in the development of precipices?



How would such jointing in the rock affect the erosive action of a glacier moving down
the valley of the Merced River?



What evidence of such action is apparent on the map ?
202



"



(



Why would a large valley glacier erode deeper than a small one ?



Since there were glaciers

in the valleys of both the Merced River and the Yoseinite Creek, why is the valley floor of

the latter now so high above that of the Merced River?



, What is the height of the upper

Yosemite Falls? . In what way have weathering and erosion since

the Glacial period combined to give the Merced River a flat valley floor?



What has been

the effect of this on the course of the river?



Why has this region been made a National

Park? :_



203



Write a short paragraph telling what scenic and physiographic phenomena you would
anticipate seeing on a visit to the Yosemite Valley.



<

204



XL VIII.— MT. SHASTA AND SURROUNDING REGION

Materials. For Each Student. — The contour map of the United States. The Shasta (Cal.) and the

Shasta Special sheets.

Purpose. To study a volcanic cone and a region of former volcanic activity.

Introduc- Mount Shasta is the cone of a volcano which has been dormant or extinct for many centuries.

tory. In the region adjoining Mt. Shasta there is other evidence of former volcanic activity. Since

the cessation of eruptions from Mt. Shasta, erosion and weathering have to some extent modi-
fied the original outline and contour of the cone. (Text-book, p. 121.)

Location of Locate the position of the Shasta (Cal.) sheet, and outline its area with ink on your

Mt. Shasta. United States map. Letter in the name of the sheet. Mark the position of Mt. Shasta with
a cross (x).

Mt. Shasta Examine the Shasta (Cal.) sheet. What is the difference in outline and topography

and the

adjoining between Mt. Shasta and the adjacent mountain regions?

region.



What is the altitude of

Mt. Shasta? How does this elevation compare with that of the

highest points in the surrounding region?

Why is Mt. Shasta a dominating feature of

the landscape in Northern California?



Assume the floor of the valley from which Mt. Shasta rises to represent the original level of
the country, and on this basis calculate the approximate number of cubic miles of volcanic

material which has been ejected to build up the cone.



Shastina, a minor summit to the west of the main Mt. Shasta summit, is a secondary
cone. What other near-by mountains are of volcanic origin, as suggested by their form or the

names given them ?

205



Topog- Make a cross section of Mt. Shasta on a line passing through Butteville and Shastina, and

If^Sluu t exten ding to the eastern edge of the map. Let one division of the cross-section paper equal
600 feet in the vertical scale. This will give a vertical exaggeration of about four times.

What is the general shape of a volcanic cone as shown by this cross section ? ,



Are its slopes, in general, steep or gentle as compared to other mountains?
Explain why they are so much steeper near

the summit.

In what way does the cross section of Shastina suggest that it is a secondary cone?



Topo- Examine the Shasta Special sheet. In what two respects does Mt. Shasta depart

graphic

details of from f t ?

Mt.Shasta. y



Suggest a reason why the shape of the lava flows very much

resembles that of the glaciers.



On which side of the cone are valleys developed most

markedly? What is the general pattern of the drainage?

Suggest a reason for the origin of the buttes

on the south side of the cone.



206



What do the place-names Cinder and Ash suggest as to the

material where they occur?



Why should the larger glaciers be on the north side of the cone ?



Write a short paragraph summarizing the topographic characteristics of a volcanic cone
composed partly of ash and partly of lava.



207



Materials.



Purpose.



Introduc-
tory.



Location
and extent
of these
regions.



XLIX. — PIEDMONT VALLEYS OF THE PACIFIC SLOPE

For Each Student. — The contour map of the United States. The Cucamonga (Cal.) sheet.
Colored pencils.

To study the formation of alluvial fans of large area, and the relation of such fans to the
adjacent topography.

The mountains of the west coast are still rising, and being, therefore, young mountains, the
processes of denudation are very active on their slopes and summits. In consequence, the
streams which flow down their slopes carry heavy loads of sediment, and the intermont areas
of this region, like the Valley of California, owe their level floors to filling up with this waste
from the mountains. (Text-book, pp. 66-68.)

On your map of the United States outline the areas of the larger Piedmont valleys of
the Pacific Slope, as indicated on the diagram map. (It is to be understood that there are
many other smaller areas of similar conditions in this region.)

Between what mountain ranges are these valleys located?



What is the approximate



area of each in square miles ?



Color in with blue pencil (using the symbol indicated in the legend square on the dia-
gram map) the areas of the Piedmont valleys of the Pacific Slope. Fill in the proper legend
square and mark it Pd. Val. Pac. Slope.

Study of an Locate the position of the Cucamonga (Cal.) sheet on your map of the United States and

alluvial fan outline its area with ink. Letter in the name of the sheet.

on the edge What is the nature of the country shown in the northern part of the Cucamonga sheet?

Piedmont

valley.

In the southern part?

What is the approximate average slope per mile of the stream in

i Cucamonga Canyon between its source and the point of its disappearance at the edge of the

mountains? What is the average slope

"209



per mile of the country for five miles to the south of the mountain base?

How do these two slopes compare in steepness?



Over which slope could the stream carry the greater amount of sediment ?

"Why would such a mountain stream be abundantly supplied

with sediment?



Why could this sediment load not be carried far beyond the edge of the

mountains?



What portion of the load (i.e. what kind of material) would be deposited

first? Why does the stream disappear at

a short distance beyond the mountains?



Account for its reappearance farther south.



What is the significance of the dotted brown patches and streamers ?



Describe the
conditions that you think would be observed in this region at a time when a great flood poured



out from the canyon.

210



Why are such deposits as these called alluvial fans 9



On what portion of their surface

are their slopes steepest? Why there?

Why do the contours bend farthest outward directly opposite the stream mouths?



Is the

climate on the alluvial fans arid or humid?

Why, then, is there such dense settlement?



What is the source of the water that these communities need ?



Human Give two reasons why the towns are located near the base of the alluvial fans and away

occupation.

from the foot of the mountains.



Write a short paragraph comparing and contrasting the mode of origin and the slopes
and topography of a delta and an alluvial fan.



211



L.— THE PACIFIC RANGES AND SAN FRANCISCO HARBOR

Materials. For Each Student. — The contour map of the United States. The San Francisco (Cal.) sheet.

The Tamalpais (Cal.) sheet. Colored pencils.

Note. — It will be well to mount the two topographic sheets on cloth so that they form one continuous
map.

Purpose. To study the physical geography of a mountain region along an ocean coast.

Introduc- The mountain systems of the Pacific Slope, west of the Columbia and Colorado Plateaus

tor y- and the Great Basin, are still being uplifted and, in consequence, have the topography and

characteristics of very young mountains. The uplift is not a simple elevation, but is made up
of a complex of movements, both up and down vertically, and including also lateral shifts of
the mountain blocks. Those parts of the region which are adjacent to the ocean show the
evidence of these movements most clearly, because the ocean furnishes a permanent level, or
datum plane. (Text-book, pp. 206, 321.)

Location On your contour map of the United States outline the region of the Pacific Ranges as

and extent indicated on the diagram map.

ofthe What parts of what states are included in this region ?

region.

What notable differences are there between the Pacific and Atlantic coasts of the United
States?

Give a reason why there is no broad coastal plain along the Pacific Coast.

How does the total area of all the high mountain provinces of the United States compare
(approximately) with the area of the plain and plateau provinces?

213



Did you, previous to taking this course, conceive the mountain regions of the United States to

be wider or narrower than you have outlined them?

What reason can you give for your answer?



Color in with red pencil (using the symbol indicated in the legend square of the diagram

map) the region of the Pacific Ranges. Fill in the proper legend square and mark it Pacific

Ranges.

Study of Locate the position of the San Francisco and Tamalpais (Cal.) sheets, and outline with

a section of j_ n ^ the area they include. Letter in the names of the sheets.

f^h° Have the mountains shown on these sheets a rugged or a gentle topography ?

Pacific

ranges. Have the streams steep or gentle slopes ?



Are the small streams tributary to any large system, or inde-
pendent? What do these facts indicate

regarding the topographic age of the region?

Is the coast line of California, in general, high and rocky, or low and sandy ?

Is it, in general, straight or indented?

What does such a large irregularity as San Francisco Bay indicate

as to the most recent change of land level in this part of the coast?

How do you account for the flats on which

Oakland and Berkeley are built ?

What is the origin of the narrow neck of land which cuts off the mouth of the Bolinas
Lagoon ?



214



What does its position indicate as to the prevailing direction of currents on this coast?



Human Why is San Francisco Bay an exceptionally favorable site on the Pacific Coast for the

occupation.

growth of cities?



How is the site affected by the fact that the adjacent mountains are growing ?



Which has the greater number of docks for ships, Oakland or San Francisco ?

Suggest a reason why San Francisco, on a peninsula, has grown more than Oakland, on the

mainland, which has more direct railroad connections.



What effect has the presence of the cities had on the settlement of the adjacent mountain

regions?

Why was a railroad built to the summit of Mt. Tamalpais?

Suggest reasons for the building of several of the

difficult mountain roads of the region.



Write a short paragraph citing the factors which make San Francisco Bay a very impor-
tant harbor.



215



LI.— COAST LINE CORRELATION

Materials. For Each Student. — The contour map of the United States. The Boothbay (Me.) sheet. The

Barnegat (N.J.) sheet. The Port Orford (Ore.) sheet.

For General Class Use. — Mt. Mitchell (N.C.-Tenn.) sheet.

Purpose. To gain an appreciation of the variation in conditions along the coasts of the United States

and the main causes for this variation.

Introduc- There are four general variations in the nature of coast lines, dependent on four variable

tory. conditions: Whether the coast line is being elevated or depressed, and whether the coast

topography is low, or bold and rugged. The length of time that a given condition has existed

also exerts a decided influence in determining the character of the coast line, as do the nature

of the adjacent land areas and the exposure to waves and currents.

Study of a Locate the position of the Boothbay (Me.) sheet on your contour map of the United States

bold, rocky, an( j outline its area in ink. Letter in the name of the sheet. (Text-book, pp. 208-210.)

indented

coast.



Topog-
raphy.



In what physiographic province is this area located ?



What was the rock structure of this province, as noted in your previous study ?



In what respects does the topography of the Boothbay area differ from that of the part of this
province previously studied?



Which has the older topography ?_

What is the most notable characteristic of this coast ? _



What is the general direction of

the extension of the long bays ("Rivers")?

Are the shores along this coast steep or low? What does this suggest

as to the depth of the water offshore ? 1

What is the approximate average elevation of the islands in, and the ridges between, the

217



long bays? Are these elevations continuous ridges

or isolated knobs? Would there be a greater or

lesser number of islands if the land surface were raised 50 feet?

If it were depressed 50 feet?

How does this apply in explanation of the present conditions along this coast ?



Why should this be called a drowned coast ?



Human Give reasons why you think this region is attractive as a summer vacation resort,

occupation.



What protection do the deep inlets afford vessels ?



Why are lighthouses necessary ?



What does their location suggest as to which is the most important harbor of this part of the

coast? Give a reason why on this coast of

many fine harbors there is no large city.



Study of a Locate the position of the Barnegat (N.J.) sheet on your United States contour map and

low, sandy outline its area in ink. Letter in the name of the sheet. (Text-book, pp. 205 and 212-215.)
coast.

°^ )g " In what physiographic province is this area located?

Is the coast line bold or low ? What is the condition of the valleys of

the larger streams?

218







Does this suggest recent submergence, or uplift, of the land along this coast ?



What would be the effect of a continued movement in the same direction ?



In the other direction ?



What is the origin of Island Beach ?



What is the nature of the small hills on its surface ?



Explain why the ocean side of Island Beach is so straight and its land side so irregular.



What do the blue-lined (straight) areas represent? (See Fig. 20.)

s. What, then, is taking

place in the bay between Island Beach and the mainland ?

Why is a hook, extending west-
ward, formed at Barnegat Light?



219



What does its position and extension suggest as to the

direction of the current which carries the sand supply?



Does the action of the currents and

waves tend to straighten a coast line, or make it irregular?

Human What evidence is given by the map that the water between the mainland and Island

occupation.

Beach is quite shallow?

r What kind of return justifies the building of a railroad to this

barren sand bar?



Give some reasons why ocean bathing is much more pleasant here than at

Boothbay, Me.



Why is this Barnegat shore especially dangerous to navigation ?



What recognition of this fact do you find on the map ?



Why are the broad mouths of the
rivers not available for harbors?



220



Study of a Locate the position of the Port Orford (Ore.) sheet on your United States map and out-

bold, reg- line its area with ink. Letter in the name of the sheet. (Text-book, p. 206.)
ular coast.

fTopog- In what physiographic province is this area located?

raphy.

What are the general characteristics of that province ?



To what extent are they shown on

the Port Orford sheet? x

What is the nature of the coast line bordering a region of rising mountains, as here
shown?



What portion of the coast line shown on this sheet rises directly and steeply from the sea ?

Which portion has the most extensive coastal

plain? How does the presence of the large

streams account in part for the coastal plain ?



What conditions of the topography of the

adjacent land areas would lead to a comparatively rapid development of a coastal plain along

this coast?



221



What does the direction of the extension of the bars along this coastal plain (and the deflec-
tion of the river mouths) indicate as to the direction of the currents along the coast?



How does the presence of the streams tend to maintain openings in the bars ? ..



: Account for

the lakes along this coast.



Human What general conditions have prevented a dense settlement along this coast?

occupation.



Account for the location of Port Orford.



What effect must the mountains have on the

future growth of such a seaport?



Why is most of the agricultural settlement found on the



northern coastal plain and in the valleys of the larger streams ?

222



Write a paragraph comparing and contrasting the conditions of the coast lines of the
three areas studied.





223



LIL — SPECIAL TYPES OF LAKES

Materials. For Each Student. — The contour map of the United States. The Van Horn (Tex.) sheet.

The Crater Lake Special (Ore.) sheet.

Purpose. To afford the pupil an opportunity to apply the methods of the preceding exercises in making

an original interpretation of the features of the above-named sheets, and to gain an incidental
knowledge of two types of lake basins.

Introduc- In interpreting the Van Horn (Tex.) sheet, see Text-book, pp. 87 and 169..

t0, 7- For the Crater Lake (Ore.) sheet, see Text-book, pp. 121-122.

Consult the references given above, and then proceed to interpret the two maps to the
best of your ability, following the general scheme of the preceding exercises.



225



(



226







Materials.



Introduc-
tory.



FIELD EXCURSIONS FOR THE SPRING SEASON

LIIL — EXCURSION TO STUDY GLACIAL PHENOMENA

For General Class Use. — One or more magnetic compasses.



Purpose. To study the nature of the evidence of the former presence of glaciers, and to note some of the

effects of former giaciation.



If the school lies outside the belt of former continental giaciation, this excursion cannot,

of course, be undertaken ; but if it is situated within the limits of that belt, the probabilities

are that several of the topics of this outline can be included in a single excursion. In some

regions two or more excursions could be profitably devoted to this study.

Glacial For this part of the excursion it is assumed that the class is taken to a rock exposure on

scratches. which glacial striations are visible. Is the rock surface between the striations rough or

smoothed? .___ What is the width of the

scratches? Are they straight or irregular ?

i What is their length ? Describe this rock

surface in a few sentences.



What kind of a surface would running water make ?

Weathering?

What agency could

cause such scratches on a rock surface? What is the compass

direction (approximately) of the scratches? From what direction

did the ice come ? What effect will weath-
ering have on this rock surface ?

From the freshness of these strive, what do you conclude

as to the recency of the glacial period?



227



Bowlders It is assumed that the class is taken to a place where one or more bowlders of foreign

and peb-

b es - origin may be seen. What is the nature of the bed rock of the region ?



.. Of what kind of

rock is the bowlder composed?

What reason can you give for the fact that such glacial

bowlders were given the name erratic ?



Do you know where rock of this kind is found in

place? Could an ordinary current of water have brought this bowlder?

What agent of transportation could readily carry so large a rock?

Does the place from which the bowlder has

probably been brought agree with the direction indicated by the glacial scratches?

A till bank. It is assumed that the class is now examining a cut in a deposit of till. In what kind of

a water current, rapid or slow, is clay deposited ? In what kind of a

water current are pebbles carried and deposited ? When water de-
posits sediment, is it assorted or unassorted ? Is it stratified or un-

stratified? Describe this deposit. I



Is it assorted?

228



Is it stratified? Would water that brought pebbles also deposit clay at

the same point? Why could water not have formed this deposit?



Could wind have caused it? Why?



Could ice have formed it?

Write a brief statement of the differences between ice and water as agencies
of transportation and deposition.



Write a brief statement giving the proof that this deposit was not made by water, but by ice.



Examine the pebbles in the till to see if they are all the same kind as the bed rock of the region.



Are any of them scratched ? Describe the scratched stones, and tell how

they could have been scratched if brought by a glacier.

229



What is the form of stream pebbles?

Are stream pebbles scratched ? What light do the scratched stones throw

upon the origin of this till deposit?



Write a paragraph stating the evidences that you have seen indicating the former presence
of an ice sheet in this region, and the reason for concluding that these phenomena cannot be
assigned to other agencies, such as wind or running water.



Other gla- If other glacial phenomena, such as moraines, drumlins, kames, eskers, or outwash gravel

cial phe- plains are studied, note their position, form, and composition. State their origin, with reasons
nomena.

for the conclusion.



230



LI V.— EXCURSION TO STUDY RIVER VALLEY DEVELOPMENT


1 2 3 4 5 6 7 8 10 12 13 14 15 16

Online LibraryRalph S. (Ralph Stockman) TarrA laboratory manual for physical and commercial geography → online text (page 10 of 16)