* * * * * MT. FAIRWEATHER (C-4) and MT. FAIRWEATHER (C-5), ALASKA, topographic quadrangles, scale 1:63,360, and AIR PHOTO PAIR 6 (58 40'N, 'W)

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1 GEOLOGY 254 Name Spring, April, 2015 Laboratory Exercise 9: Glaciers and Glacial Landforms The purpose of this lab is to familiarize you with some of the aspects of modern glaciers, as well as landforms created by glaciation on both local, alpine and continental scales. I've also appended a few maps and air photos from karst regions. A few "review-type" questions on features we've seen previously are also included to help keep you sharp! * * * * * MT. FAIRWEATHER (C-4) and MT. FAIRWEATHER (C-5), ALASKA, topographic quadrangles, scale 1:63,360, and AIR PHOTO PAIR 6 (58 40'N, 'W) The North Crillon Glacier is a large valley glacier in southeastern Alaska that fronts in a marine fjord in Lituya Bay, where a small delta is forming. Except for the valley-wall confinement, this may represent a modern analogue for the Belgrade esker and delta complex you visited in GE141. The presence of the delta suggests an esker may be presently forming here as well - why? Note the lateral moraines along the margins, in the upglacier section on photo 6L, as well as the longitudinal ridges on the surface of the glacier. Note the steep front of the ice where ice calving is active adjacent to the delta, and how this section of the glacier is differentially retreating. The crevasses here are forming as a result of the increased shear stress in the ice that is fostered by the calving and removal of frontal support. Note also the sudden break in slope on the mountainside above the glacier, and the smaller alpine glacier that lies in a hanging valley above this break in slope. That break in slope represents the level of the ice at the last glacial maximum extent, probably in the "Little Ice Age" that culminated in the last years worldwide. In 1874, in fact, the North Crillon Glacier was much more extensive and joined the La Perouse Glacier near the terminus of the latter. Rapid melting since that time has resulted in retreat of the terminus, uncovering the valley now occupied by Crillon Lake. Lituya Bay itself is a fjord, a deeply scoured glacial channel now below sea level. What is the maximum water depth shown in Lituya Bay? feet

2 GE254: Glacial Features Laboratory VALDEZ, ALASKA AND VICINITY - special map sheet, scale 1:62,500 (1930) This map is interesting from both a glaciological and historical point of view. First of all, note that the entire map was surveyed on foot in (note in lower left corner). Note as well that Valdez Arm in the lower left is a fjord of impressive scale: the average slope to the ridge crest in the mountains to the west is about 45 degrees! The brown lines on the Columbia, Shoup, and Valdez Glaciers are medial moraines, features formed by what set of circumstances in the glacier flow? Note also that the Columbia Glacier itself is damming two small lakes; as you might expect, ice-dammed lakes don't tend to be very stable features. We'll look at the net result of the sudden draining of one such ice-dammed lake at the end of this lab. Note the position of the town of Valdez, as shown on the map. What would you expect to be the general nature of the geological substrate here? As you should expect, this did NOT prove to be very stable during the 1964 Alaskan Earthquake, and Valdez was destroyed. The town has been rebuilt just north of the bedrock ridge 4 miles to the west. This location becomes of environmental concern when you realize that the southern end of the trans-alaska oil pipeline lies on the south shore of Valdez Arm. The Columbia Glacier is now undergoing relatively rapid retreat by calving, dumping large quantities of icebergs into the chilly waters through which the oil tankers carefully sail. The EXXON VALDEZ ran aground in March, 1989, while trying to avoid one of these bergs, dumping an estimated 11 million gallons of crude oil into Prince William Sound. In GoogleEarth, go to 61 10'N, '30"W. What difference do you see here compared to what shows on the map before you at these same coordinates?

3 GE254: Glacial Features Laboratory DEMARCATION POINT, ALASKA topographic map sheet, scale 1:250,000 This map sheet displays a portion of the eastern end of the Brooks Range of Alaska, that northernmost extension of the Rocky Mountains, at the Canadian border. What is the contour interval? What is the predominant drainage pattern shown by the Kongakut River south of 69 degrees 25 minutes north latitude? What does this imply about underlying geologic structure? What is the drainage pattern and obvious geomorphic feature that lies immediately south of Demarcation Bay, down to about 69 degrees 30 minutes north latitude? Drainage pattern: Landform: This is a region that has been repeatedly and extensively glaciated throughout Quaternary time (the last 1.68 million years). Note the dozens of small modern glaciers in the southwest portion of the map. Note also the relatively flat bottoms of most of the larger stream valleys, with steeply rising valley walls on either side. These are U-shaped valleys on a grand scale. A major reflection of the dominance of glacial erosion in the histories of these rivers is that virtually all of the major channels become extremely choked with sediment (sand and gravels) and incredibly braided as they emerge from the mountain front. Are the lower reaches of these rivers (the Jago, Aichilik, Egakshak, and Kongakut in particular) presently aggrading or degrading their channels and floodplains? What would you expect to be found beneath these areas, as a geological substrate?

4 GE254: Glacial Features Laboratory MOUNT RAINIER EAST, MOUNT RAINIER WEST, MOWICH LAKE, and SUNRISE, WASHINGTON topographic quadrangles, scale 1:24,000, and AIR PHOTO PAIR 5 - Carbon Glacier, Mount Rainier, Washington The Carbon Glacier is one of 17 glaciers flowing off the flanks of Mount Rainier, which has more individual glaciers than any other single mountain peak in the conterminous United States. Note the cascading ice as this glacier flows down a stepped valley profile, the debriscovered surface once you get below the equilibrium line altitude (E.L.A.), the aretes and horns near the terminus, and the crevasses indicative of modern movement in the ice. Note also the extreme turbidity in the Carbon River where it flows out from the terminus - a debris-choked stream loaded with glacial flour. Find the Carbon Glacier. Note particularly also the Emmons Glacier and the Nisqually Glacier. The former is the largest glacier (in terms of total ice volume - over a cubic mile) in the conterminous United States; the latter, one of the best studied. Note the areas mapped as dead ice terrain and unstable ground fronting these glaciers, respectively. The dead ice terrain fronting the Emmons Glacier was still underlain by considerable ice when visited by Professor Donaldson Koons of this Department (whom I replaced in 1982) in 1961; most of that ice was gone when I visited the same site in The terminal moraine representing the Little Ice age maximum (in the late 19th Century) fronting the Emmons Glacier is approximated by the foot contour; this same glacial maximum extent is indicated in front of the Nisqually Glacier by the unstable (stippled) area that terminated at about the highway bridge across the Nisqually River. MOUNT McKINLEY NATIONAL PARK, ALASKA special map sheet What are the scale and contour interval? Scale: C.I. One inch on the map is how far in real distance (mi or km)? This is the highest mountain peak in North America, at 20,320 feet (6100 m). It also has the greatest local relief of any terrestrial mountain on Earth - some 18,000 feet (5500 m) visible from the north at Lake Minchumina. The numerous glaciers flow around jagged peaks - nunataks - which would be horns if the area were deglaciated completely. Note the asymmetric distribution of glacial ice on the mountain. The principal moisture source nourishing these glaciers lies in what direction? How long is the Kahiltna Glacier, from Mount Capps to the terminus (in miles AND km)? miles; km The broad U-shaped valleys clearly indicate that the late Pleistocene ice maximum lay far to the south of the boundaries of this map sheet. In the north, the distribution of kettles shows somewhat less clearly that the northern ice limit may be roughly approximated by the 2000-foot contour. The kettles are concentrated in belts across the mountain front of the Alaska Range here; the scattered, irregular lakes throughout much of the lowland farther north are thermokarst

5 GE254: Glacial Features Laboratory lakes, formed by thawing and collapse of ice-rich permafrost in the region. We'll look more at thermokarst lakes and periglacial features in lecture towards the end of the semester. YOSEMITE VALLEY, CALIFORNIA special topographic sheet, scale 1:24,000, and Air photos GS-VJS, frames and The air photos here available unfortunately show only the lower portion of Yosemite Valley; El Capitan is the most readily recognizable landmark. The valley itself is the archetypical glaciated U-shaped valley, with steep valley walls rising (in the case of El Capitan and Half Dome) nearly 3000 feet. The northwest face of Half Dome, long thought to be the result of glacial scouring, is actually a structurally controlled feature, representing the trace of a significant fault in the granodiorite of the Sierra Nevada batholith. Note the hanging valleys and the resulting waterfalls here as well: Yosemite Falls, Snow Creek Falls, Sentinel Falls, etc. How did these form?

6 GE254: Glacial Features Laboratory MT. KATAHDIN, MAINE topographic quadrangle, scale 1:24,000, and Air photos GS-VFDO, frames 3-29 through 3-31 This is a set of photos you've already seen. Locate and identify examples of each of the following alpine glacial features: Cirque: Tarn: Arete: Horn: Moraine-dammed lakes: GRAYS PEAK, COLORADO topographic quadrangle, scale 1:24,000, and Air photos GS-VDOM, frames and This particular air photo pair shows vividly a number of examples of rock glaciers, which are glaciers with exceedingly heavy loads of rocky debris that can be considered to be essentially moving taluses. These will look in aerial photos as if they had flowed down the mountainside like soft, overly thick frosting on a warm cake. How many can you identify in the Stevens Gulch drainage? What, as glacial features, are Mt. Edwards, Grays Peak, Torreys Peak, and Grizzly Peak?

7 GE254: Glacial Features Laboratory What kind of pond sits at the head of Chihuahua Gulch, and what would you call the basin in which it is situated? Pond: Basin: Note that the Continental Divide runs across this quadrangle. This is the drainage divide between the Atlantic and Pacific drainages; Grizzly Gulch and Stevens Gulch drain into Clear Creek, which eventually flows into the Atlantic through the Mississippi drainage and the Gulf of Mexico. Chihuahua Gulch and the other streams south of the divide all eventually wind up flowing westward, probably as tributaries to the Colorado River system. ELMIRA, NEW YORK topographic map sheet What are the scale and contour interval? Scale C.I. What are the latitude and longitude of the southwest corner of the sheet? Latitude Longitude [Map sheets at this scale are commonly referred to as 1 degree by 2 degree quadrangles, because they measure one degree of latitude by two degrees of longitude; they are also referred to as 1:250,000-scale quadrangles, for the obvious reason.] This map sheet displays the Finger Lakes of western New York State in their entirety. These are glacially scoured, bedrock-basin lakes that are an extremely impressive sight from the air. (One of the major air routes between Boston and Chicago passes just to the south of this area.) Note that Cayuga and Seneca Lakes are on the order of 40 miles long each! Given that the bedrock in the upper portion of the map sheet (at least) is fairly flat-lying Paleozoic sedimentary strata (predominantly limestones and shales), what do you believe is the most likely explanation for the fact that the major lake troughs seem to radiate out fanlike from a common central point that would lie off the northern margin of this map sheet?

8 GE254: Glacial Features Laboratory HIGHLAND PARK, ILLINOIS topographic quadrangle, scale 1:24,000 [You will probably find it advantageous to look at this and the Mendon, Illinois quadrangle at the same time.] The most obvious thing that should stand out first on this map sheet is the general tendency for most of the major topographic trends to parallel the modern shoreline of Lake Michigan. The steepness of the shoreline itself implies that the deposits here are reasonably compact and will stand in near-vertical faces without collapsing, although undercutting of the shore by storm waves is certainly a contributing factor. Note the steep slope that parallels the shoreline at a distance of about one mile, sloping away from the lake. The broad ridge between this slope and the lake is a Woodfordian (late Wisconsin - about 14,000 years old) moraine formed by the Lake Michigan Lobe of the Cordilleran Ice Sheet. The till deposit underlying this moraine has been assigned to the Wedron Formation in this area. The ridge paralleling this one, which runs through the central part of Deerfield, is another, slightly older moraine ridge. The trough in between (now well marked by the red line of the Skokie Highway and Edens Expressway) was undoubtedly a meltwater channel for at least a short period of time in the Quaternary history of this area. The clay pits between Deerfield and Northbrook are situated on deposits of a Pleistocene lake older than the modern Lake Michigan but younger than the moraines. Note in general that the drainage in most areas is not particularly well integrated. MENDON, ILLINOIS-MISSOURI topographic quadrangle, scale 1:62,500 This area, to the southwest of Highland Park, lies along the western border between Illinois and Missouri. Note how sharply defined the limit of the Mississippi River floodplain is here. In the eastern half of the map area, note how well-developed the dendritic drainage is, particularly in contrast to that of the Highland Park quadrangle. This difference in the degree of drainage development is a useful relative age-dating technique when working with glacial deposits, since you would expect that older deposits will show more post-depositional erosional modification. The ridge that underlies the Crescent School (top margin, center) is the crest of a moraine of Illinoian age (about 135,000 years old), and most of the rest of this eastern map area is underlain by glacial deposits of roughly the same age, overlain by a mantle of younger (Wisconsinan) loess up to 2 m thick. SEATTLE, WASHINGTON 1 o x2 o map sheet - scale 1:250,000 The most conspicuous features on this map sheet are the Olympic Mountains on the west and the Puget Sound on the right (home of the giant octopus!). The Olympics were extensively glaciated during the Pleistocene by alpine ice, and there are numerous small glaciers present today as well. Lake Quinault, for example, is dammed by a broad, low terminal moraine. The Puget Sound itself is a glacially scoured feature; geologic evidence indicates that prior to about 15,000 years ago, it was a broad alluvial floodplain. What is the deepest contour you can find underwater in the Sound? Depth

9 GE254: Glacial Features Laboratory The southern ice limit here is approximated by the broad, arcuate trend of Interstate 5 from Tacoma to Olympia. In the southern part of the Sound, the tendency for the drumlinoid hills here to fan out from the central portion of the valley, paralleling what would be expected if a previously confined glacier (the Puget Lobe of the Cordilleran Ice Sheet, confined between the Olympic and Cascade Mountains on the west and east, respectively) flowed out into a region of relatively less confinement in a giant piedmont lobe. During deglaciation, the ice still blocked the northern end of the Sound, creating a large ice-dammed lake that filled the basin and that then spilled over through the lowland where Elma and McCleary are located, draining directly into the Pacific Ocean through a river system southwest of this map area. PHIPPSBURG, MAINE surficial geologic map, scale 1:24,000, by G. W. Smith Printed air photo pair from Belgrade GE141 Field trip This map displays, in a spectacular fashion, what have to be a classic example of washboard moraines along the Maine coast, in the area just north of Popham Beach. These kinds of features would be very difficult to pick out on the ground without a tremendous amount of work, and much of this mapping has undoubtedly been done using air photographs. Compare these to the photo pair from near Belgrade; use a small pocket stereoscope to view the circled examples of washboard-like moraines on that air photo pair. CLYMAN, WISCONSIN topographic quadrangle, scale 1:24,000 Drumlins, drumlins everywhere! Once you've seen them on a map, they jump right out at you. It's very easy to get a clear idea of the direction of movement of the last major glacial advance through this area. In the space below, sketch and label an accurate north-south topographic profile along the long axis of the drumlin on which the Fehling Cemetery is located (southern margin of Sec. 11, T10N, R15E). Put north on the left of your profile, and LABEL both axes clearly! What characteristic stands out sharply as regards steepness of slopes as it relates to the direction of ice movement?

10 GE254: Glacial Features Laboratory SODUS, NEW YORK topographic quadrangle, scale 1:24,000 More drumlins and drumlinoid hills, this time from western New York State. These are quite distinctive, however, from the features in Wisconsin. For one thing, these glacially produced ridges are higher, with steeper slopes, and a smaller length:width ratio. These may well be, at least in part, bedrock-cored features, and thus not true drumlins as I use the term. ABSARAKA, NORTH DAKOTA topographic quadrangle, scale 1:24,000 Given that virtually all the topographic relief here is due to late Pleistocene glaciation, two dominant patterns clearly indicate the nature of the underlying deposits. The western half of the map is underlain by hummocky glacial till, a terminal moraine complex, while the eastern half of the map sheet was undoubtedly the contemporaneous outwash apron. This extremely characteristic pattern may be seen along much of the Laurentide ice margin in the western half of the midcontinent. RIVERHEAD, NEW YORK topographic quadrangle, scale 1:62,500, and Air Photos GS-VEWK, frames 2-2 through 2-5 This map covers an eastern section of Long Island and beautifully shows the landforms that were created by a terminal moraine and its associated outwash fan, as well as a second recessional end moraine and its fan. In the space below, construct a topographic profile at a horizontal scale of 1:125,000 (i.e., half the map scale) from Roanoke Landing in the north, through Riverhead to Quiogue on the southern coast. Put north on the left side of your profile and use the vertical scale that's given here, in feet: 240 ft ft ft ft ft ft... 0 ft...

11 GE254: Glacial Features Laboratory On the profile, you should now be able to pick out the extent of the moraines and the associated outwash aprons. Indicate the likely trend of these in the subsurface, to make your topographic profile into an approximated structure section through the geology of this part of the island. What is the approximate vertical exaggeration of your profile? V.E. = X * * * * * FEATURES PRODUCED BY THE SPOKANE FLOODS OF GLACIAL LAKE MISSOULA FOSTER COULEE, WASHINGTON topographic quadrangle, scale 1:24,000, and Air Photos NHAP82, frames and You have already seen some evidence of the late Pleistocene floods from Glacial Lake Missoula in Montana, in the area around Moses Lake as well as Babcock Bench along the Columbia. Those floods, which resulted from the lake breaking through a dam of glacial ice, scoured much of this area down to the surface of the Columbia Plateau Basalts that underlie the entire region. This portion of Washington State is known as the Channeled Scablands, and Foster Coulee is one of the channels that is responsible for that name. It was one of the major channels that carried part of the flooding; close inspection will reveal giant ripple marks on the modern valley floor. EVERGREEN RIDGE, WASHINGTON topographic quadrangle, scale 1:24,000, and Air Photos NHAP82, frames and (47 01'30"N, 'W) Frenchman Coulee, in the southwestern part of the map, is one of many such features also produced by the Spokane Floods of Glacial Lake Missoula. Although there is not a well-defined coulee inland from this canyon that is comparable to Foster Coulee, this nevertheless was a grand (if short-lived) waterfall each time the flooding recurred - very likely comparable to present-day Niagara Falls. Note that the walls around the Coulee average 300 feet in height, and that contour lines often "pinch out" on the north and eastern sides - indicating vertical cliffs. Babcock Bench, the cut terrace (as opposed to a fill terrace!) along the Columbia we saw earlier in the semester, lies at about the same elevation as the floor of Frenchman Coulee, and is still some 300 feet (90 m) above the modern water level of the Columbia River! Note that the main highway cutting NE/SW across the map area is U.S. Interstate 90 (the western end of the Massachusetts Turnpike). The small community 4 miles northeast of Frenchman Coulee (visible on the air photos but outside the map area) is the small town of George, Washington - whose only restaurant is, naturally enough, Martha's Inn.