areas of landslides 12 30 - department of mineral …...parshall 100k sheet, north dakota adjoining...
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Sanish N e w T o w n S a g
Twin Buttes
Mandaree
Spotted Horn
Keene
Johnsons Corner
Croff
Bu rnt
Creek
D e e p
C r e e k
L i t t l eM i s s o u r i
R i v e r
C h a s eC r e e k
North Ki lldeer
C o r r a l C r e e kMountain
Jim C ree
k
L A K ES A K A K A W E A
C r e e k
M o c c a s i n
S q u a w
C r e e k
S k u n kC r e e k
Skunk Cree k B
ay
S a ddle ButteBay
Hi datsa Bay
McK enzi e Bay
Squaw Creek Bay
Mocca s in Creek Bay
Wolf Chief Bay
Wa ter C hief Bay
M edi c
ine S ton
e Bay
Re d Butte
B ay
S i x m i l eC r e e k
Arikar a Bay
Cha rg ing C re ek
Deepw ater Creek B ay
D e e p w a t e r
C r e e k
She ll Cr eek Bay
V A N H O O K A R M
S h e l
l
C r e e k
F o r k
E a s t
S h e l l
C r e e k
Sa n ish B ay
Reunion B ay
Muskra tLake
L i t t l e S h e l l C r e e k
Drags W
olf Ba
y
Hunts A long Bay
Four Be
ars B a
y
C l a r k sCreek
North Fork
No rt h Bra nch Clea
r C re ek
Clear
Cr eek
M a l n o u r i e C r e e k!(8
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MCK ENZIE COUNTYDUNN COU NTY
MOUNTRA
IL CO
UN TY
MC KENZ
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UNTYMOUNT RAIL COUNTY
DUNN COUNTY
DUNN
COU
NTY
MERC
ER C
OUNT
Y
M CLE AN CO UNTY
MER CE R CO UNTY
MCL EAN COUNTY
DUNN CO UNTY
L A K E S A K A K A W E A
L A K E
S A K A K A W E A
IndependencePoint
B l u e B u t t e s
FORT BERTHOLD
RESERVATION
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MOUNTRAIL COU NTYMCL EAN COUNTY
Parshall
New Town
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103o 00 '48o 00 '
102o 00 '48o 00 '
103o 00 '47o 30 '
102o 00 '47o 30 '
100K Series: Prsh - l North Dakota Geological SurveyJohn P. Bluemle, State Geologist
Edward C. Murphy2003
R. 96 W.
T. 15
2 N.
T. 15
0 N.
T. 14
8 N.
T. 14
7 N.
T. 14
9 N.
R. 94 W. R. 93 W. R. 92 W. R. 91 W. R. 89 W.R. 90 W.
R. 96 W. R. 94 W.R. 95 W. R. 93 W. R. 92 W. R. 91 W. R. 90 W. R. 89 W.
T. 15
1 N.
Cartographic Compilatio n: Elroy L. K adrmas
Geologic Symbols
UNIT DESCRIPTIONS
QUATERNARY
R. 97 W.
RECENT/PLEISTOCENE
R. 95 W.
A mass of sediment and/or rock that have slid or tumbled down s lope. A pink area on the map my represent dozens of individual landslides.
Landslide
Surface geology undifferentiated
Qls
Known contact between two geologic units
Adjoining 100K MapsParshall 100K Sheet, North Da ko ta
General Information on Landslides Landslides are masses of rocks and sediment that have tumbled or slid down a slope under their own weight. They constitute geologic hazards that can damage buildings, roads, railroad tracks, pipelines, transmission lines, and other types of infrastructure. Landslides are generally characterized in the field by steep, near-vertical slopes (the scarp) that are upslope from a mound of displaced rock (the body). The body of the slide may be relatively intact or it may be severely fragmented. Recent or relatively new landslides are generally characterized by a fresh (well-exposed rock) scarp and a sparsely vegetated body. Older slides are typically more difficult to identify in the field because the scarps may be covered with vegetation and the landslide bodies are often well-vegetated, covered by mature trees.
Landslides are most readily identifiable from the air. The landslides mapped on the Parshall Sheet were identified from a set of aerial photographs (1:20,000 scale) that were flown between May and September of 1958. It is unfortunate that these photographs were taken when leaves were on the trees because groves of leaf-bearing trees tend to obscure landslides, especially small ones. On the other hand, leaves can sometimes make it easier to identify these features. Trees and bushes are often aligned within very distinct parallel-, transverse-, and/or semi-circular-depressions that generally occur within the body of the landslide. The roots of vegetation can help to stabilize landslide areas. Slopes fail for various reasons including the steepness or angle of the slope, rock type, bedding, and moisture content of the rocks. Most landslides in western North Dakota are rotational slumps that have a well-defined head and toe. Typically, the part of the slope that breaks apart slides down the slope as a single unit and the beds tilt back in the direction of the slope. The failed mass of rock is, however, almost never a cohesive unit; tension cracks generally cause the failed material to splinter into smaller portions. Successive landslides may occur at the same location. Over time, the accumulated material from multiple, adjacent landslides can cover an area that is several thousand feet wide and several miles long.
The Parshall Sheet Most of the area of the Parshall Sheet is underlain by the Sentinel Butte Formation (Paleocene), which consists of alternating beds of sandstone, siltstone, mudstone, claystone, clinker, and lignite. A veneer of glacial deposits covers much of the upland areas. In the area covered by the Parshall Sheet, landslides are most prevalent within the Little Missouri River Badlands and the drainages along the west side of the Missouri River Valley between New Town and Independence Point. The rocks in these two areas are generally no different than those outside of these landslide-prone areas. Landslides are most prevalent along the Little Missouri River Valley and this short segment of the Missouri River Valley because both were carved relatively quickly (in geologic terms) when glacial ice diverted the Little Missouri and Missouri River into and through these areas. Approximately 600,000 years ago, glaciers blocked the path of the north-flowing ancestral Little Missouri River near the west border of the North Unit of the Theodore Roosevelt National Park. The glacier forced the river to turn east and carve the steep, rugged badlands in this area. As a result, the older, north-trending segment of the Little Missouri River badlands (Marmarth to Grassy Butte) is wider, with gentler slopes than the younger, narrower east-trending segment covered by this map sheet. Therefore, landslides are less common in the Little Missouri River badlands from Marmarth to Grassy Butte.
Similarly, a glacier blocked the path of the Missouri River near New Town approximately 14,000 years ago. Prior to that event, the Missouri River had flowed for tens of thousands of years through the New Town Sag creating the valley that is now occupied in part by the Van Hook Arm of Lake Sakakawea. The old channel (Van Hook Arm) is about five miles wide in contrast to the much younger, present-day channel to the west, which is only about one mile wide. The old and new channels converge at Independence Point. The new, steep slopes of the rapidly carved channel are highly susceptible to slope failure as are the rapidly cut ravines and coulees between Blue Buttes and the western edge of the Missouri River Valley. Landslides are so prevalent near the mouth of Bear Den Bay that both Lewis and Clark noted them in their journal entries of April 14, 1805. Over 2,400 landslides were identified and are plotted on the Parshall Sheet. Many of these slide areas are complexes that contain multiple landslides that may have occurred over a long period of time. These slides cover an area of 35,000 acres or approximately 4 % of the total land mass of this map. More locally, landslides occupy up to 30 or 40% of the Little Missouri River Badlands and the Missouri River Valley and associated drainages in the Blue Buttes area. Landslide areas may extend along valley walls for more than four miles and can exceed one-half mile in width. Most of these landslides are well-vegetated indicating they are quite old, perhaps thousands of years old, near Bear Den Bay and tens, if not hundreds, of thousands of years old in the Little Missouri River Badlands. Slope failure likely occurred relatively quickly after the steep-sided badlands slopes had formed. In these areas, careful consideration is required prior to construction to avoid landslide prone areas. Construction activities can reactivate landslides that have been stable for hundreds or thousands of years. Furthermore, the presence of numerous landslides in an area (such as the Little Missouri River Badlands and the Missouri River Valley southwest of New Town) generally indicate widespread slope instability necessitating extreme caution be used when building on ,or adjacent to ,slopes anywhere within that area.
Scale 1:100,000
Mercator Projection 1927 North American Datum
Shaded Relief - Vertical Exaggeration 9x
0 1 2 3 4
Miles
Standard parallel 47o 45' Central meridian 102o 30'
Areas of LandslidesParshall 100K Sheet, North Dakota 1982 Magnetic No rth
Declinatio n at Center of Sheet
12o 30'
Other Features
MarshWater - IntermittentWater
Paved Road
River/StreamStream - Intermittent
E Section CornerCounty Boundary
Tribal Boundary!(8 State Highway
Unpaved Road
Landslides identified on this sheet were mapped from stereo pairs, black and white 1:20,000 scale aerialphotographs flown between 6-6-58 and 9-7-58. As a result these maps can be used to identify areas thatare vulnerable to slope failture, but are not an up to date assessment of all lands lides for the area.