In the summer of 1962 a completely portable and relatively simple electrically heated thermal core drill of new design was constructed and used to obtain 16 oriented samples of ice 2.5 cm. in diameter by 120 cm. in length from depths ranging from 12 m. to 137 m. in lower Blue Glacier, Mount Olympus, Washington, U.S.A. The thermal element is a 0.260-in. (0.66-cm.) diameter 300-W. 150-V. tubular heater bent to form an annulus with an external diameter of 5.0 cm. Opposed ratchet-like teeth break off and hold the core inside the tubular core barrel. Orientation is recorded photographically by a commercial inclinometer modified to show azimuth and to be controlled from the surface

Kamb, W. B.

Shreve, R. L.

Caltech Authors - Main

INSTRUMENTS AND METHODS 
PORTABLE THERMAL CORE DRILL FOR TEMPER ATE 
GLACIERS* 
By R . L. SHREVE 
(University of California, Los Angeles, C alifornia, U.S .A.) 
and W. B. KAMB 
(California Institute of Technology, Pasad ena, California, U .S.A.) 
ABSTRACT. In the summer of 1962 a completely portable a nd rela tively simple electrica lly heated the rma l 
core d rill of new d esig n was constructed a nd used to obtain 16 o rien ted sam ples of ice 2· 5 cm. in d ia m eter 
by 120 cm . in leng th from depths ranging from 12 m . to 137 m . in lower Blue G lacier, M ount O lympus, 
W ashing ton, U .S.A. The thermal element is a 0· 260-in. (0·66-cm .) diamete r 300-W. ISO-V. tub ula r hea ter 
ben t to fo rm a n a nnulus with a n externa l dia meter of 5' 0 cm. O pposed ra tchet-like tee th brea k off and hold 
the core inside the tubula r core ba rrel. O rien ta tion is recorded p ho tographica ll y by a commercia l inclino-
meter modified to show az imuth and to be controlled from th e surface. 
R ESUME. Dura nt 1'ete 1962 un carotteu r thermique electrique entierement por tat if, rela tivemen t simp le 
e t de conception nouvelle, a ete construi t. On I'a utili se pour o btenir 16 echantillons de glace ori entee ayant 
2,5 cm de diametre e t 120 cm de longueur pour des profond eurs a llan t de 12 a 137 metres dans la pa rtie 
inferi eure du Blue G lacier , M oun t O lympus, Washington , U.S .A. L 'element therm ique (300 W , 150 V ) 
tubula ire de dia metre 0 ,66 cm, a ete courbe pour former un a nnea u de d iametre ex terne de 5 cm . D es 
encliquetages a dents opposes, cIetachen t et tiennent I'echa ntillon a I' in terieur du tube carollier. O n en-
registre photographiq uem en t I'orientation a I'a ide d 'un inclino m ctre commercia l modifi e de fa c;:on a donner 
I' azim uth et a etre con t r61e a partir de la surface. 
ZUSAMMENFASSUNG. Im Som mer 1962 w urde nach neuen E n twurfcn ein tragbarer und relati v einfa chcr 
thermischer Kernbohrer m it elektri scher Beheizu ng gebaut. D a mit wurden 16 o ri entien e E ispro ben m it 
einem Durchmesse r vo n 2,5 cm und einer L a nge von 120 cm a us T iefen zwischen 12 m und 137 m im un teren 
Blue G lacier am 1\1t. Ol ympus, Washing ton , USA , erboh r l. D as thermische E lem en t ist ein rohrenformiger 
H eizkorper von 0,66 cm Durchmesser m it 300 W Leistung bei 150 Volt, del' so gebogen ist, dass e r einen 
Ring mit 5.0 cm Aussend urchmesser bildc t. Gegenstand ige Sperrza hne brechen d en K ern ab un ci h a lten 
ihn im Inneren des R o hrgehauses rest. D ie O rientierung wird pho tographisch m it e inem ha nd elsublich en 
Incl inometer festgeha lten , d as so abgea ncl cn wurde, dass es a uch clas Azimut a nzeigen und von de l' Ober-
Aache a us bedi ent werclen kan n. 
I NT ROD UCTION 
Core drilling to obta in samples from deep within glaciers is a logical adjunct to study of 
the ice a t the surface. It makes possible, for example, investigation of g lacier structure in 
three dimensions, m apping of structure a nd other features under perma nent snow cover , 
measurement of texture a nd fabric of tempera te glacier ice tha t has undergone ra pid deform-
a tion without subsequent annealing, a nd analysis of oxygen-isotope ra tios a nd of entrained 
matter , such as gases, pollen grains, a nd rock pa rticles, in the ice a t depth. 
Samples have been obta ined from a d epth of severa l hundred meters in the cold , dry pola r 
ice of G reenland and Anta rctica, by bo th mecha nical a nd thermal core drilling (La ngway, 
1958, p . 33 7; Pa tena ude a nd others, 1959, p. 1- 4; R agle and others, 1960, p. 1- 4) ; but, 
because of its great weight, bulk, a nd cost, the equipment required is unsuited for the 'wt 
uncommon glaciological research projects in which everything must be tra nsported on m en's 
backs. At the opposite end of the sca le of portability, the ha nd-operated SIPRE coring a uger 
(Anonymous, 1957, p . 30) has been widely used with g reat success; but for holes deeper tha n 
a few m eters, especia lly in water-sa tura ted ice, the effort required for its use increases very 
rapidly with depth ; m o reover, it obta ins an unoriented core. O ther co re drills for sampling 
* Publication No. 29 7 o f the Institu te of G eophysics, U niversity o f California , L os Angeles; Pu blica tion 
No. I 174 of the Division of G eological Sciences, California Insti tute of T echnology. 
11 3 
SA 
114 JOURNAL OF GLACIOLOGY 
glacier ice have been reported (Miller, '951, p. 579 ; Schwarzacher and Untersteiner, '953, 
p. "3 ; Ward, 1952, p. I 17; 1954, p. 433) ; but, in general, glaciologists have rather 
surprisingly neglected the development of this potentially highly useful tool. 
This paper describes the design and performance of a completely portable and relatively 
simple electrically heated thermal core drill that was employed in the summer of 1962 to 
Core bar rel 
Tubular heate r 
He x - socket 
head scre w 
Teflon liner _--"'F===!"""" 
0 
E=3 
0 
5 
E"3 E=3 E=3 
2 
E="'"3 
"-- - Core ba rrel 
Teflo n liner 
Spring 
Tooth 
10 cm 
E"3 I 
3 4 in. 
I 
Fig. I. D etails of construction of thermal core drill. Left: E xterior. Right: Longitudinal cross-section 
obtain oriented samples of ice 2·5 cm. in diameter by 120 cm. in length from depths ranging 
from 12 m. to 137 m. in lower Blue Glacier, Mount Olympus, Washington, U.S.A. Structure, 
texture, and fabric of the cores were studied; they will be discussed in a separate article 
(Kamb and Shreve, 1963 [a], Cb] ) . 
DESIGN 
In addition to achieving the primary objective of obtaining, from depths as great as 
300 m. in temperate ice, oriented samples big enough to permit measurement of foliation, 
texture, and fabric with statistical assurance, the design of the core drill had to satisfy a 
number of secondary conditions. The core drill had to be as simple, and use as many existing 
or ready-made components as possible. It had to operate on the power supplied by an 
existing 2,500-W. 230 j II5-V. portable powerplant. It could be no more than 5.0 cm. in 
diameter, so that it could pass through holes bored with existing hotpoints which will be 
described in a forthcoming paper on bore-hole operations and observations on Blue G lacier, 
Mount Olympus, Washington, by R. L. Shreve and R. P. Sharp. Finally, it had to be rugged 
and capable of being transported in light ski-equipped aircraft or carried on foot over rough 
terrain . 
The design finally developed after considerable laboratory testing and modification is 
shown in Figures I and 2. Thermal drilling was chosen for its simplicity and its proven 
effectiveness in water-saturated ice, and to facilitate getting oriented cores. The thermal 
element is made from a 0 · 260-in. (0· 66-cm. ) diameter 300-W. ISO-V . General Elec-
tric " Calrod" tubular heater with stainless steel jacket bent to the desired shape. The 
ends of the heater are sealed with ceramic plugs cemented with a hard, heat-resistant epoxy 
resin and coated with synthetic rubber. The finished element has high mechanical strength 
and long operating life, and can withstand temporary operation out of water. The thermal 
element is mounted on the lower end of the core barrel , a piece of stainless steel tubing 
(5 .0 cm. external diameter, 4·' cm. internal diameter) 120 cm. long which receives the 
con, as the drill penetrates the ice. 
I NSTRU M ENTS AND METHODS 115 
A m ajor difficulty in developing the core drill was to prevent melting of the newl y formed 
-core b y hot water convected up into the core barrel from the thermal element. This was 
solved by the teflon (polytetrafluorethylene) liner, which both inhibits convection in the 
lower end of the core barrel a nd impedes conduction from the core ba rrel to the water inside. 
T he liner causes the water on the outside to be warmer tha n that on the inside. This effect 
T ri pod -----.;~i£!:;.~ 
Non-coring 
Inclinom ete r 
Limit switch 
Winch 
wire 
ubber coati ng 
ore barrel 
ubular heater 
Teflon lin er 
Core drill 
Ice core----------~~~~;-__ 
Fig. 2 . Portable thermal core drill . L ift: Thermal element and lower end of core barrel . Photograph by L. W~)'mollth . V/)/)er 
right: Ceneral arrangement of core drill and slIrface equipment. Photograph b) , R . L. Shreve . L ower right : Removal of core. 
Phologra/)h by ]. IU. Shreve 
was utili zed to minimize melting even further ; a la rge hole in the upper end of the core 
barrel a llows a convec tion cell to develop in which warm water fl ows up the outside and cool 
water down the inside. 
As the core enters thc core barrel , it passes between a pair of opposed ratchetlike stainless 
steel teeth that permit it to move upward but not downward. When the core drill is raised, 
the teeth , whose sha rp points quickl y pressure-melt into the ice when drilling stops, penetrate 
the core and break it off. To release the core after it is brought to the surface, the tee th are 
retracted b y means of a pair of hand-held hooks made of heavy music wire. 
116 JOURNAL OF GLACIOLOGY 
A sliding cylindrical weight inside the core barrel rests on top of the core and holds it 
down on the teeth to preserve its orientation relative to the drill. Though successfu lly used, 
this system presents practical difficulties in operation, especially if the core is broken, as is 
often the case. Ideally, the drill should make a narrow groove or other permanent mark of 
known orientation running the full length of the core, but a practical method for doing so 
was not found, despite a considerable amount of experimentation. 
Mounted on the upper end of the core barrel is a limit switch assembly consisting of a 
mercury switch that shunts a 200-Q 200-W. wire wound resistor across the thermal element 
when the core barrel is full. It is designed to operate properly even if the axis of the core 
drill is ti lted as much as 40 degrees from the vertical in any direction. The resultant increase 
in current serves as a signal that drilling is completed. 
Located just above the limit switch assembly is a Parsons single-shot inclinometer that 
records photographically the positions of a compass needle, a pendulum, and, as modified 
for the core drill, an azimuthal mark indicating orientation of the core barrel. The inclino-
meter is a lso modified to operate on electric current supplied and manually controlled from 
the surface, rather than with the regu lar internal batteries and timer, thus assuring a good 
record every time and permitting measurement of orientation after drilling is complete. The 
inclinometer is capable of measuring azimuths to within 2 degrees and inclination up to 
4 degrees from the vertical to within o' I degrees. With shorter pendulums it can measure 
inclinations up to 27 degrees with the same relative accuracy. 
The core drill (20 kg. ) is attached to a o· 32 cm. diameter galvanized steel aircraft cable 
300 m. long ( 14 kg. ) which is raised and lowered by a hand-cranked winch (32 kg. ) mounted 
on a wooden tripod (100 kg., can be disassembled) . Current for the inclinometer is carried 
by a two-conductor rubber-covered cable ( 15 kg. ). Power for the core drill is supplied by a 
commercial portable 2,500-W. 230/ 1 15-V. 60-cycle generator driven by an integrally mounted 
two-cycle gasoline engine (55 kg. ) and is transmitted to the drill by two single-conductor 
rubber-covered cables (25 kg. each ). 
PERFORMANCE 
In late August 1962 the core drill was set up beside a crevasse on Blue G lacier, Mount 
Olympus, Washington, U.S .A., from which samples at a few meters depth could be obtained 
with pick and saw, and was used to drill a vertical hole 5 m. deep, from which four cores 
2' 5 cm. in diameter by 120 cm. in length were obtained. The three primary objectives of 
drilling this preliminary hole were ( I) to find the best operating routine, (2) to develop a 
system for preserving the orientation of the cores during handling, and (3) to verify that the 
structure, texture, and fabric of the cores are unaffected by thermal drilling. 
At a depth of 5 m. the drill penetrated the crevasse, allowing the water to drain from the 
hole. The resultant over-heating did not affect the thermal element, which was operating at 
rated power, 300 W., but it did cause warping and partial destruction of the teflon liner, 
which had to be replaced. 
In early September the core drill was moved to another site; and a hole 137 m. deep was 
drilled, reaching the bed of the glacier. With a power input of 300 W. the COl"e drill penetrated 
the ice at I ' 2 m. hr. - 1; it was used alternately with a non-coring thermal drill whose speed 
was about 8 m. hr. - 1. The hole drilled was about 5' 5 cm. in diameter, and remained within 
one degree of vertical at a ll depths. 
No special operating difficulties were experienced, although great care had to be exercised 
to prevent jamming of the four cables in the hole. For safest operation the weight of the core 
drill should exceed the combined weight of the cables as much as possible. Sixteen cores were 
obtained, fourteen of them oriented. The two failures were due to lack of emulsion on an 
inclinometer record and to operator error respectively. Most of the cores were somewhat 
INSTR UMENTS AND METHODS I 17 
elliptical in cross section, and showed irregular variations in diameter probably attributable 
to fluctuations in efficiency of drilling. Many of the cores were broken into 2, 3, or 4 pieces, 
which nearly always could be unambiguously fitted together. Modification of the operating 
procedure to minimize disturbance of the drill during coring noticeably diminished, but did 
not eliminate, breakage. Increasing the internal diameter of the core barrel, to increase 
clearance around the core, and insulating the bottom of the sliding weight, to prevent 
pressure-melting and wedging of the core, might further decrease breakage, but unfortunately 
could not be tried. Finally, it is possible that cores brought suddenly from depth in a glacier 
will break spontaneously regardless of how gently they are handled, so that no change in 
equipment or procedure would be entirely successful. 
A CKNOWLEDGEMENTS 
This work is part of the lower Blue Glacier research program direc ted by Professor R. P. 
Sharp of the California Institute of Technology. It was supported by the National Science 
Foundation (Grant Gq688) and by the University of California (Grant No. 1694) . The 
National Park Service graciously gave permission for the field tests, and personnel of Olympic 
National Park aided the project in numerous ways. Mr. William R. Fairchild, of the Angeles 
Flying Service, Port Angeles, Washington, provided logistical support. Mr. William Parsons, 
·of the Parsons Survey Company, South Gate, California, kindly supplied the inclinometer, 
modified it to record azimuth, and provided vital consultation on the other changes required. 
Professor C. R. Alien and Mr. Curtis Bauman contributed generously to the success of the 
core drill, both in the laboratory and on the glacier; their invaluable assistance is warmly 
appreciated. 
MS. received 16 July [963 
REFERENCES 
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Geophysical Union , Vol. 44, No. I , p. 103. rAbstract.] 
Kamb, VV. B., and Shreve, R. L. 1963[b]. T exture and fabric of ice a t depth in a temperate glacier. Transactions. 
American Geophysical Union, Vol. 44, No. I , p. 103. [Abstract.] 
La ngway, C. C .,jr. 1958. Bubble pressures in Greenland glacier ice. Union Giodisiqlle et Giophysiqlle Internationale. 
Association Intemationale d' fJ.ydrologie Scientifiqlle. Sy mposium de Chamonix, / 6- 24 sept. [958, p . 336- 49' 
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Schwarzacher, "V. , and Unters teiner, N. 1953. Zum Problem d el' Banderung des Gletschereises. SitZllngsberichte 
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Instruments and Methods: Portable Thermal Core Drill for Temperate Glaciers

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Instruments and Methods: Portable Thermal Core Drill for Temperate Glaciers

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