GEOLOGICAL SURVEY CIRCULAR 46 

May 1949 

INTERPRETING GROUND CONDITIONS 


FROM GEOLOGIC MAPS 


Prepared by the 

Geologic Division 

eVetCe 

ge .1.0 • 

o CO 

e0.9` e-c ,i)eo .y,Nso 

QE 

.U58c 

No.46 

1949 


75 
LiSRARrj 

Bureau of Reclamation 

Denver, Colorado 

e 

QE 

75 

.u58c 

#46 

U.S. Geological Survey. 

Circular 46. 

UNITED ERIOR 

WASHINGTON, D. C. 

Free on application to the Director, Geological Survey, Washington 26, D. C. 

GPO D FS0 9.22.49 250 BOOKS 
BUREAU OF RECLAMATION DENVER LIBRARY 

1. 1M11111111111111 

92026537 

INTERPRETING GROUND CONDITIONS 


FROM GEOLOGIC MAPS 


Prepared by the Geologic Division 

Intelligent planning for heavy construction, water supply, or other 

land utilization requires advance knowledge of ground conditions in the 

area. It is essential to know: 

1) the topography, that is, the configuration of the 


land surface; 


2) the geology and soils, that is, the deposits that 


compose the land and its weathered surface; and 


3) the hydrology, that is, the occurrence of water 


whether under or on the ground. 


These elements usually are considered in planning land developments that involve much investment; detailed surveys generally are made 

of the topography, geology, soils, and hydrology at the site selected for 

development. Such detailed surveys are essential, but equally essential 

and often overlooked is the need for general surveys prior to site selection. 

Only if the general surveys have been made is it possible to know 

that a particular site is most suitable for the purpose and that no situations in the tributary areas that might affect the project have been overlooked. Moreover, the general regional relations must be known in order 

to properly interpret the geology, soils, and hydrology at a particular 

locality. In brief, both the general and the specific are needed in order 

to avoid costly mistakes either during or after development. 

The accompanying maps illustrate how a general geologic map can 

be used for interpreting grc .d conditions during a planning stage prior 

to site selection. The topographic and geologic maps, which provide the 

basic data, have been simplified from some existing ones. The interpretive sheets are intended to provide some examples of the kinds of 

information that trained persons can read from such basic maps. 

UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY ALPINE QUADRANGLE 

0 9 RG W 

4i' 

- — -

4500-� 41 

0 

I_ I_ I_ I_ 

5 Miles 

I 

Topographic maps show quantitatively the configuration of the 

land surface. This is accomplished by drawing contours that 

represent level lines on the earth's surface. Irregularities in the 

contour lines reflect the ground plan shape of the land forms; 

the spacing between the contours measures the amount of slope. 

In addition, topographic maps show the works of man, such as 

roads, railroads, and buildings, and drainage features such as 

perrenial streams, intermittent streams, springs, and marshes. 

TOPOGRAPHIC MAP 
 

CC 

UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY ALPINE QUADRANGLE

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EXPLANATION 

Young fan deposits; gravel, with admixed 


sand, silt, and clay. 


Pleistocene 

Lake Bonneville depos its ,___

___d•_____

--, 

Q bsi Qbc:%;'' 

Gravel member; Sand member; Silt member; Clay somber; 


gravel and sand clean sand; forms lake bottom lake bottom 


in delta deposits. offshore bars and deposit. deposit. 


C 74C1 delta deposits. CO3 = SO3 Cl
 op 4 50 1F-ci
 °3 5°3 3 3
 CO3>S0 iLci 


3
 

Old fan deposits; bouldery gravel with 


admixed sand, silt, clay. Considerable 


caliche in upper layers. 


U 

CL 

BedroCk; mostly limestone, some quartzite. 

Fault; dotted where concealed. 

GEOLOGIC MAP 
UNITID STATES DEPARTMENT OF THI INTERIOR 

ALPINE QUADRANGLE OtOLOOICAL SORVIV 

N, 'WVA‘� •,•\ 

•••••••• N1/4N•NN$& •••., \‘‘ • •••••••sv 

• • N••.; 

/////////// 

FIRST EVENT: 

These ancient rocks 

folded and faulted 

upward to form 

mountains. 

THIRD EVENT: 

This fault became active; 

5-10 feet of movement before 

Lake Bonneville time; fault 

extends under lake beds and 

FIFTH EVENT: 

This fault again 

active; 20 feet 

of displacement. 

may have recurrent movement 

anytime. SIXTH EVENT: 

This fan and the small one 

3 miles west were built on 

SECOND EVENT: 

This fan built of 

gravel etc. eroded 

from mountain. 

top of Lake Bonneville 

deposits after the lake had 

disappeared. These poet.. 

Bonneville fans are still 

being built. 

FOURTH EVENT: 


Valley inundated by glacial Lake 


Bonneville. Delta of gravel (Qbg) 


built at mouth of Alpine Canyon. 


Shore currents moved sand (Qbs) westward on delta and in bars in front of 


delta. Silt (Qbsi) deposited near-


shore; clay (Qbc) deposited offshore. 


These lake deposits are underlain by 


the pre-Bonneville fans which represent 


the second event. 


READING GEOLOGIC HISTORY FROM THE GEOLOGIC MAP 
UNITED STATICS DEPARTMENT OP INS INTERIOR

OKOLOMDAL SURVEY 


�
 ALPINE QUADRANGLE 

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 N\� 410A

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!Miles 0 I� 1� 

Hard rocks. Good source for limestone or quartzite for building stone, riprap. Quarry 


operations would require drilling and blasting. Limestone suitable for cement. 


2 	This gravel is angular but silty; poorly graded and contains considerable secondary line; 


not suitable for concrete aggregate; poor source for road metal. 


3 	This gravel well rounded and well graded but contains considerable line; not suitable for 


concrete aggregate; excellent road metal. 


4 This gravel poorly graded; fragments in part angular and in part well rounded; deposit is 


free of secondary lime; best source for concrete aggregate. 


Clay deposit contains lime and other water-soluble salts; fair source for structural clay; 


good source for seal clay; not suitable for high grade ceramic purposes. 


THE GEOLOGIC MAP AS A GUIDE TO CONSTRUCTION MATERIALS 

5 
 

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UNITED STATE® DEPARTMENT OF THE INTERIOR

010LOGIOAL SURVEY 	� ALPINE QUADRANGLE 

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K Miles 
 s 


A Clay ground; poor surface drainage; no subsurface drainage; road metal and fill for subgrades 


must be hauled from area B or C. Ground easily excavated by power shovel or dozer operation. 


Will require aubdrains. 


Gravelly and silty ground; fairly adequate surface and subsurface drainage. Good foundation 


for roads or buildings. Basement excavations must be shallow to avoid intersecting the groundwater perched on the underlying impermeable Lake Bonneville beds. This area lies across the 


projection of one of the recently active faults (see E). 


Gravelly ground with excellent subsurface drainage; ground easily excavated by power shovel
 C or dozer. Excellent road foundation; the deposit rests against one of the recently active 


faults so buildings should be constructed to withstand shocks of intensity 8, R-F scale (see E). 


Sandy ground underlain by silt at depths less than 8 feet; good surface drainage down to the
 D silt. Easily excavated by hand tools. Basement excavations must be shallow to avoid intersecting groundwater perched on the silt. Good foundation for roads but clay is needed for 


binding sand. 


Two recently active faults. Movement on either one may be renewed at any time causing earth-
 E quakes. Buildings within a mile or so of the faults or their projection should be constructed 


to withstand shocks of intensity 8, R-F scale. Five miles from the faults the shocks would 


not be expected to exceed intensity 5. 


THE GEOLOGIC MAP AS A GUIDE TO FOUNDATION 


AND EXCAVATION CONDITIONS 

UNITED lams ogrARTIAINT OF THE INTERIOR

OKOLOW0AL SURVEY 

0 

A B 

This old fan Groundwater is 

deposit under,- perched on the 

lies all Lake impermeable lake 

Bonneville beds 10-15 feet 

deposits. It below the suris an aquifer face of this 

that can be young fan 

reached by deposit. This 

drilling in groundwater 

the south part however is 

of the area. subject to 

pollution by 

town sewage. 

owor,,ex'sp,w,o, , I' 

r,A.:•"410, :707,07/40X, ,,••• r 

5 Miles 


C 

Zone of seeps 


at edge of 


young fan 


deposits where 


shallow groundwater (see box 


B) emerges at 


surface. 


Seeps polluted. 


ALPINE QUADRANGLE 

Moderate 


quantities of 


good quality 


groundwater 


available at 


base of this 


delta deposit, 


about 40 feet 


below surface. 


THE GEOLOGIC MAP AS A GUIDE TO PROBLEMS OF UNDERGROUND 


WATER SUPPLY AND SANITARY ENGINEERING 

UNITED STATES IMPARTMENT OP THE PRI1r1111;011 

GEOLOOMAL SURVEY ALPINE OfiALYRARELE 

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O 

Permeability and 


Area elope of 


Impermeable; 


I elopes steep. 


Moderately 


permeable; 


2 elopes moderate 


Nigbly permeable, 


gentle slopes.
 3 

Moderately 


permeable;
 4 low slopes. 


Impermeable 


and ground
 5 nearly flat. 


• ////// /I', // ,,,, ,i l'el) ,„4"/ iZiiZ i.i0;‘,1'7 .,,400, 

-,,., 

/////////////, , • 

Swat 


condition, 


Maximum 


coefficient 


of runoff. 


Little runoff 


during moderate 


storms; considerable 


runoff during severe 


storms. 


Practically no 


runoff even 


following most 


severe stores. 


Moderate runoff 


during severe 


storms. 


Inter steads in 


pools for long 


periods after rains. 


II 
 %!%i% 

,, 4///// 

5 Miles 4W __J 


41ty,.. /OA 


'Wood control, drainage and 


canal problems 


Principal source of floods that 


would be hazardous in valley. 


Subject to floods from canyon; 


during severe storms may discharge 


floods from surface runoff. Moderate 


seepage losses can be expected from 


canals. 


Mo flood control problem. 


Reservoirs and canals require 


sealing to avoid excessive 


seepage losses. 


Subject to flash floods from 


canyon.c
Moderate seepage losses 


can be expected from reservoirs 


and canals. 


Ground readily flooded and 


difficult to drain.c
Mo seepage 


losses from reservoirs or canals. 


XLewer limit of perennial flow in streams draining mountain. 


THE GEOLOGIC MAP AS A GUIDE TO SURFACE WATER PROBLEMS SUCH AS 

FLOOD CONTROL, DRAINAGE, CANAL CONSTRUCTION ETC 

4 
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY ALPINE QUADRANGLE

alb 

Qbs 

• 	 ,• ff/fi lat 

ijr/ / .M‘leii5TOP7 472r 

4, i i/// � 

,= /;/=„,_ , Are7 ////// // ///70,.

4/'/;04/W/ 
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11 

9	1M!*‘/
 //////// /// ////// //////////

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0 4 5 Miles

L 1 	 J 

Mountainous area; soil generally thin and stoney. Locally there is a fossil soil having 10 foot 


of leached clay (an excellent source of structural clay). Principal watershed supplying valley 


area. Forested. 


2 	Stoney and in part bouldery ground. In places covered by fossil soil (See 1); locally the 

leached clay has been eroded exposing strongly lime-enriched gravel and silt. 

Stoney ground. Top foot is brown windblown silt containing well rounded gravel; common large
 3 size 1 - 2 inches diameter. Five to ten feet of lime-enriched gravel beginning a foot below 


the surface. 


4 Clean quarts sand; grains -114 mm diameter, well rounded, stained by iron-oxide. No silt matrix, 

some lime carbonate cement. Locally blown into low dunes. 

5 	Stoney ground, silt matrix. Slightly lime-enriched sone less than a foot thick nadir surface 

layer of leached silt and gravel 6 inches thick. 

6 Silt ground. Contains about 3% of water-soluble salts -- 1.5% of calcium carbonate and 1.5% 

of sulfates and chlorides of sodium and potassium. These salts leached from top 6 inches, and 

redeposited in next foot. 

Clay ground. Contains about 4% of water-soluble salts -- 1% of calcium carbonate and 3% of
 7 sulfates and chlorides of sodium and potassium. These salts locally form surface crusts around 


moist depressions. 


THE GEOLOGIC MAP AS A GUIDE TO SOILS AND 


LAND UTILIZATION PROBLEMS 

DATE DUE 

GAYLORD PRINTED IN U.S.A.