HALL / 187

LAKE

K. HALL / 187

U'l N

~ a::w

~ u_~

;:) 0

-, z

on ^lI)

...

, E;:3

btlC .;:

c..'"

...c w

ow a::w U~

~

lI) U'l

more rapid snowmelt than shaded areas.

Within the nivation site these factors, together with the microtopography, result in a great variation between exposures of number, amplitude, and wavelength of freeze-thaw cycles at the rock surface.

Figure 5 shows the temperature curves obtained on four rock outcr"ops at the eastern end of the stone pavement area (Figure 3). Curves A and B, obtained from the vertical faces of the outcrops, appear similar while C, from a basal niche, is much subdued, and D, from a horizontal surface, indicates a radical difference in temperature conditions during the latter part of the record. Specific details of the number, wavelength, and amplitude of the freeze phases illustrated in Figure 5 are given in Table 2. It can therefore be seen that there are very big differences in freeze-tha~temperature conditions among these four points.

Locations A and B both experienced nearly the same duration of freeze time, but B experienced one more freeze-thaw cycle than A and had 40 % overall lower freeze amplitude (Table 2). Location C experienced approxi- mately 25 % fewer freeze-thaw cycles than A or· B, nearly 100 h less total freeze time and had the smallest mean freeze amplitude of all four locations. The thaw phases appear fairly similar between C and A or B (Figure 5) but the freeze phases do not, those of C being greatly subdued with respect to either A or B.

This difference is believed to result from the thermistor at location C being situated at the very back of a semienclosed basal niche where there would be a greater stored body of heat to be overcome than on the exposed vertical face.

Location D, a horizontal surface (Figure 3), indicates the effect of snow cover. From 20 October (Figure 5) the snow on top of this site appears to have remained at a sufficient thick- ness to effectively damp out. the freeze-thaw cycles experienced at the other points such that, for the duration of the record shown, location D experienced 57% fewer freeze occurrences and 60 % less total freeze time than location A. At the end of the available record, curve D is approaching O°C (±0.2°C), and data obtained in the spring of the following year indicate a rock surface temperature at this point of - 1.1 QC. While the dampening effect of the snow cover at point D is important with respect to geomorphological implications, it is important to note that during the period D was snow free it experienced the 188/ ARCTIC AND ALPINE RESEARCH

\ 1973

SEPTEMBER OCTOBER

I ,15,

" ,20,

!I ,

(SI roll,

^{I ,}⁵ , I I I "¹⁰ ^,15,

a

^{, I}

·C .5

'51-'0

F 0 -15 F -5 ·5

G 0 G

-10

FIGURE6. Six-hourly rock surface temperature records for thermistors E to F,located on the backwall, during the autumntowinter period.

largest mean freeze amplitude and the longest total freeze time of the four points, although not the largest number of individual freeze- thaw cycles (Table 3).

Figure 6 shows the temperature curves obtained from three locations on the backwalI

(Figure 3). Locations E and G are on the vertical face while F is at the base of a vertical crack 0.2 m wide, 1.8 m long, and 0.45 m deep. As with the rock outcrops, the three positions on the backwall show variation in number, duration, and amplitude of freezes K. ^{HALL /} 189

TABLE2

Freeze occurrences~onitored by therrnistors A to D on rock surface outcrops during the period 12 September to 10 December 1973

A ^B C D

Amp(°C) Wave (h) Amp(°C) Wave (h) Amp(°C) Wave (h) Amp(°C) Wave (h)

- 2.0 36 - 1.0 12 -0.2 6 -0.8 18

- 3.2 18 - 1.3 18 - 0.3 12 - 3.5 36

- 1.3 12 -1.5 18 - 0.3 12 - 4.2 24

-4.5 36 - 0.2 12 -0.9 12 -1.7 12

- 2.9 12 -0.6 6 - 0.2 6 - 5.0 36

-3.2 18 - 2.0 18 -4.2 132 - 3.2 30

- 2.7 18 - 1.3 12 - 2.8 24 - 3.5 36

- 3.6 24 - 1.9 6 -6.8 216 -1.1 18

-0.8 18 - 1.8 12 -1.1 12 -11.4 402

-9.0 108 - 1.4 18 -0.9 12 n = 9

-2.0 18 - 6.3 108 - 0.2 6 x Amp = -3.8°C

-11.0 240 - 3.2 18 - 1.5 18 (s = 3.17)

- 1.0 8 - 3.9 18 -4.2 60 Total freeze = 612 h

-0.9 12 - 8.7 216 -4.0 48

-0.6 12 - 1.2 12 -9.3 840 +

-3.0 24 -1.1 18 n = 15

-6.9 60 -0.5 12

x

Amp - -2.5°C

-7.4 48 -2.2 18 (s = 2.76)

- 14.6 576 - 5.0 60 Total freeze = 1416 h

- 16.4 204 + - 5.5 48

n = 20 -12.0 840+

xAmp - -4.9°C n = 21

(s = 4.63)

x

Amp - -3.0^oC Total freeze - 1502 h (s = 3.01)

Total freeze = 1490 h Definitions:

Amp (OC) - Maximum freeze amplitude.

Wave (h) = Maximum freeze wavelength.

(Table 4) during the record available. Loca- tions E and G are fairly similar in response to temperature changes, but location F experi- ences 33% fewer freeze-thaw cycles and a smaller mean freeze amplitude. Detailed consideration of curves E and G show that there is 25% difference in mean freeze amplitude and that G experienced one more freeze-thaw cycle while E had 42 h more total freeze time.

The quintessence of the data is that the freeze-thaw environment within the nivation site is complex and shows great variability.

The situation becomes even more complex when temperature curves for the downslope outcrops (Figure 5) and the backwall (Figure 6) are compared for their overlap period (14 September to 21 October). Clearly, the backwall and outcrops do not experience the same regime, even within an area as small as that 190/ARCTIC AND ALPINE RESEARCH

under study, due to the variability of microre- lief and exposure to the climatic elements. The rock outcrops did not register the two cold phases of 21 September to 3 October and 5 October onwards which were so evident on the backwall (Figure 6). Conversely, the earlier fluctuations appear to have been more severe on the outcrops than the backwall.

During the two main cold periods experienced on the backwall, the outcrop surfaces in fact indicate peaks of warm temperatures; at the time of these peaks there was a comple- mentary rise of backwall temperatures, although they remained negative (S - 3°C).

Other data show that during the same period ground-surface temperatures in the lower area did not remain negative but experienced warm peaks similar to the rock outcrops.

Thus, in this instance, it is suggested, the

(1-1 Septemba1022Octooa) during which 10catlOTl D wasJTIOWJree

:\ B C 0

:--J umber of freezes 1+ 16 9 9

;( freeze temperature - 3.+ oC - 2.3°C - 1.9°C - 3.H0(:

s freeze temperature 302 2.25 231 3.I;

-'J'J +32 6I'~

:'-iumber hours offreeze 5i8 ^{J __}

T-\BLE

+

FfCI::.e occurrences rrltJTlitored OTl the backwall by thermistors E to G during the pmod U ,:,eptember to'.22October19i3

E F G

Amp(0C) W;j\'e (h) .\mp(OC) 'vVave(h) .\mp(oC) Wave (11\

- +5 2+ - 12 18 - 30 24-

- 14 18 - 0.'2 6 - 18 t5

- 0.5 6 - 03 6 - 0".J 6

- '2.6 18 - 0.9 30 _- 1 .,_.J _ti

- 18 2+ - +.6 306 -1.1 1'2

- 2.2 18 - +.2 +02 - '2.2 12

- 0.7 12 - 0.+ 6

- 9.2 29+ - 6 7 '25R

- 1+.0 396 - 2.+ 36

- 110 +0'2

:Ylean freeze amplitude at E = - +.1°C(s = +.5i);n = 9.

Mean freeze amplitude at F = - 19°C(s 1.98);n 6.

:'¥[ean freeze amplitude at G = - 3.0°C(s = 3.3+);n = 10.

Total hoursoffreezear E = 810.

Total hours offreeze at F = 768.

Toral hours of freeze at G = 768.

Detinirions:

.\mp(OC) = freeze amplitude(QC).

vVave (h) ⁼ freeze wavelength in hours.

higher outcrop temperatures are a result of heating by direct insolation (as with the ground). while the lower backwall tempera-

tures derive from the concinual shadowin~,·1·

fect there.

DISCCSSIO~

Two principal aspects of the freeze-thaw regime emerge: first. monitoring of air temperatures is no indication of temperature fluctua- :ions occurring at the rock face and. second, :hat within a nivation site verv large differ-

~nces in freeze-thaw regime occur from point () point. unfortunately. man:: investig'ations

of freeze-thaw activity are based upon mcf/"' orological station air-temperature recoph which often imply a rigorous regime with"

spring peak (Fraser, (959). As has 0<:<:(1 shown. ho"'e\'er, a nivation site is Very lik,·i:.

to be protected bv a thick snow cover 'du rifI

<

the spring period and so the geomorpholOl(i<::,J K. H\I.II I'I!

I I,

;"';)"1"( 11',.'\!t'11'. t1( lilt, .lll-·:t'IlU)I·r:ll~lr{· ll11l'(U,t-

"':'1' ,1111)(':11' il1 1)<' 111IIlil1l:d.· ..\1 Ih,' 11i\':lli,,"

\il'·. 1'(1;'(; tlllllT'll1'; It"1 Iheil' "11<\\ ,',l\('I" hi,'!' Ih~ln ^{tho,;r In} l!1e"1lI'I'''UIl(!in~ ;l!'l';t, :lIld :I\':li1-

"hit-"t!)';Iltl\\, lempCl';\IUI'C dat;\ do nOI :tppe;,l'

I I I inJic:lh: (rL'c:::c-th~l\\' ~lc~i\'i{~ (iurin~ 'pnn~.

-rhus it !~ "u~~t:S{I.·li :h::[. dcspilt' thl' Llrf~c numbt'l'111'rl'ee;:e-!i~,t\\ ^1'\,-le,; mOIliIO!'l'C! in rhe

.lIr. ~h('^-.;pri:1!! pe:·j(i(: l~ r~\)l ^.JI1 ~lCtl\T ^llITIC ^fiJI'

![":Cl.c-l!1:I\\· 'l,cdb~i":l' ^:Ii ,ill' ['(xl-; '11I'l':1n' , ,-\!Ihou~h cial.:t Pl'ruilliI1~' ¹⁰II:mpel':.ItUl'!' con- c!i(i{)n~:lnd \·J.r~J.til)i-::-::u -...jepth \\"jthin ~hL'rtlck :.lIT :lh';l'nl. lht' inrOr:~~;llionI)n roCk-I':ICl' Il':l1-

;)I'r~llurt:S dllLS l)ITcr J. :'(J.nin~ point 1'01' (he

~'(1I1sidcra[l()n^01' frC:::'':-l:~J\\' :.~)(~: dl's[ruc:inn ctlmo:lI':lble \\'irh :~1,),1 n!i1er Ilcld 1e.~,

(;~rc·Jnl"!·. !~)6~) ^t1^l" ::lOln':uory (c.:z .. ^POllS.

1('71)) in\·<:sliC:~llions.

\\·irhin-sitl· \':ll'i:llic':i ,d' t'r<:I'::I' ,'CCUITl'nce, (!l!r:l1~{he:ll:rL:fT:n ~1t"h:;'sinrl':-, ~)ri\)r^tClthl' L·~

::lr)iishnlL':1( ut' t:lt' :'e:J.~lH~;.t!,jlC)\\ ,,'()\·cr. pnl- (iul"" ;I l'ol1lolc:\ proi)i,'m. Ti1l' 11bsel'\'cd chal'-

.U·{(':-o! dll~ :\·t·~·:.:(··-!~l,l'.\ :···~!nll'^:li t~l(.' 11!\';lii()11 :"IIIL'i~ dt';)l":~l:'~'::: ~l;)\';~^'.\^:1l';'C :L·:npl':·;.ttt.::·l·~,lr~' 1l1'\I\\rored. \L.l,'\imuf~l !·;l'el.l' amplitudl' 11:1,

!In'n considerl'd b\· ,ome :.IS one 01' thc ll1:.1in I':tuors in ;i~l' deSlrUc,i\'l' fllcchanism (Gl':t\\'l', lll:;til ;lllc! "Tt this \·J.r;l" bl,t\\'\'en - I'~"C for IOC~llil\ll [';tnd - +.:2°C Il)r location F on till' same datl' t~:2 Ocober)-;I 70r; \'ari:lI\on.

Similarl\', cOll,ider:.ltion ot' Ihl' la,;1 rree:~l' n'- corckci i'or loclIion, ,-\ :.Ind C .t;i\'\:,; ,.I 7.1 °C dille!'enn' in :.Implituul', I!' number Ill' fnTl.l' ,1CCUITI'nccs i, considered ;\ m:ljO[- 1':tClllr il\

!·l'!Tl.t'-1 h:\\\':'c;i\·i t \. "Sciu!'i'n, 1iJT.!: Tilt^H11:,';, J9jR) thl'n monitorinc- ot'!ocalion 0 in,;te:ld,>/.

K\\'ouid h.:t\·l' "ut;c-l'st~d 9sulncro o,;cilbtio/lo;

imte:.ld or '2!. "Comparable \'ariation,; 1'01' c!ur:llio!l ot' I';'eez,' :.It", t'CUII' IT:ll;k,'2and -r, Thus, whether .:tmpiitude, duration, or num- bl" or i'rt'eze, i" considered [0 be rhe mo,1 irn- portanl t'acror in freeze-rha\\' rock destruction, cllt' e,rimation ot' acti ..·ir\ for a panicular ni\·:.I- ti(ln sire could be ~read\' in error it' onh"

linllleci "bse:Tation, ;"ere~b{:tinecl.

!r i,; app;,rent Ih.:tt rn:eze-t1l::lW aeri\'ir\' :11 :l

ni\·:.Iti"n silt'i"e,'\tremeh' l'omple:\ and rhal the

\\ ickh held \!;enerJ.liz:.ltions or its place \\'il!lill

ni\':lIion :lre in nced of r('\·il'\\. 1I is ;\ dil'lic,:!;

pl'l)bkrn and \'ariablcs olher rhan II'rnpt'!':1I111-"

l1uClII;ltions must be consiclered, [, is :, iJ:1,':,- dox Ih:.lr the uppermosr seoions of rock :~I\'l'S (Ih",;t' t'lrsll(J be exposed from bl'ne:llh,I r.lt:il- i nli ,;no\\, COver and last If) ht' ,no\\' cm'<:l'cdI

which experience the lirl'~lIe';l number "I' rrel'l.e-tha\\' c\'eles shoulcJ ,IH1\\' I"s,; re\( l-; elt:- 'Iruuion than' OCCUrS:.ll Ihl' rnck b:l';c Ilhl' :'11'"

l'm'l'red and last e:\p0';l·c!). :\"\'l,rthell'S' th,' e:\~en,i\ebasal niches with their apron of:'''ch:

debris sho\\ that destruqion is more potent :11

Ihe rock base, This phenomenon is perhaps rdated 0 moisture a';aibbilit\· but it Still be", :he question, as e:\Dounded

b\:

White \107ti~,

whether Ihe destru~ti\'e mech~nism^{is freeze-}

rhaw or, perhaps more likel\', hydration ,hal- lCr:nS-,

\"hile the a\'ailable data :.Ire inadequall' for det:.liieci consideration or the ['()ck-bre:.lkdll\\n mechar\lsm, a number of comments and 'lh- ser';arion,; pertaining 10 rreeze-tha\\ :tul\'il,,' l':l;~ bl.' In:t<:l' The {t'rnl ··!'n·t'::t'-i!:;l\\'" i:n:,j;···

:l'nlpC:'~llure ilueru;lliuns :tnu,;s till' ():e 1',,- therm, hu I \'arious mi ni mu m nl'Cl'"an' frlT::e amplitudes, 1'01' the I'reeze to be e1lecti\t' in terms or rock destruction, h:t\T been ';Ut;'

~esled ^b\' IaboralOr\' \I1\'estl~:lllons: ^- ^j

:'C

(Collins, 19++), -PC (Fukacb, 1~171),

- JOC (Fukacla, 197'2), - 5~C (Latridou, 1~(71),and - 610 - 10⁰

e

(Dunn anc! Huder.

1YG61. Cunsiderarion or Figure j shows Ih:ll

«)\\·:trds rhe ends orcun'e~:\, H, .:tnd C tem- p,:r:llures I1UClU:IIl' from slron"h' nl'~:Jrl\":

I'\pPJ'()~:. - j-r"C) to onh' .iust nt'c:;III\'e ( - IUlcC), Thus there arc l1uCtUalions acro,~

the \·~trI0US rhrt'shoid temper:.llUreS cir::d ,\bm'!':dthou~hno posiri\'e lemper:.lture i~ at- L1ill\'d. Tit\., Illlplin till' !J"s,ibiiil\ l!l;r; ..

['reeze-rha\\ clTecl i, taking placl' \\ilh lTll"- in~' ^{l l i}I!'l' l'llnsidl'l'cd bouncb,,' \';I!Ul' dUI'in~

the pl'!'i(Jd :hat rempl'r:.ltures ·rem:.lin b"lcl\\'

()OC. T!11' impiic:1ti~ns of this .:tre Iworulc.i:

t'lrsl. lh:1t :l ne~.:tti\·e crossinc- of (l°C must :\r' tain the critiC:.J1 \,.:tiue befol:::: il c:.ln be considered an ::I'fecli\'e freeze and, second, that the temoerature nl'l'd' nOI "0 positi\'l' 10 l'!lect Iherrt't::~e-rh:1\\^anil1n, ^{" ,}

CO:\CLLSIO:\S

:1' tlll' _1~1O\(ani\'(, lime in terms orre,ck iJr,.-:lf,- c!()\\n :)UI t'\'idence :I\'aibble from ;his Sfllli\

,u~ge,rsilll' :lU(Ull1n-\\,intt:I' periocJ ((, I)l' nl<>r"

(,2Il,dil:lli':I' impressions nl' thl' rrl'eze-lh:J\\' 1":~!I11I'^:11 ^:t ni\·:.Ition ,irl' an' in need uf rl'con- .,ickr:tlilln, Sprint; h:.l' usualh- been posruLul'd ,

_]...0.-....__ _{- -}

_...

_{_-.} _{__}

._~..,---._...-- - - -

important. Air temperJ.cure records an:

limited indicacors of temperature conditions prevaili ng at the rock face and so are ot' doubt- t'ul use in judgment of geomorphological activity. Within the nivation site:: there is a gre;H range of localize::d frec::ze::-thaw e::nvironme::nts such that great care must be:: e::xc::rcise::d in incer-

pretation whe::n information is avaibble from a limited number of poincs. The possibilit':· that a freeze-thaw action' is taking place without positive crossings of the O°C isotherm needs more detailed investigation and. if pro\·en.

adds a further complicating faccor co the:: inter- pretation of temperature records.

AC K:--iO\VLEDGM E0iTS This work constitute::s part ot' my :VI. Phi!.

undertaken through the Geographv Depart- ment. Universitv ot' Reading. tinanciallv sup- ported bv a L'niversitv Research Board Scholarship. Field facilities and logistics were kindly provided Iw the Okstindan Research Project under the super\'ision ot' Dr. Peter Worsley. Thanks are due co the manv project workers who helped in various ways in the lidJ. particularlv S. Bridges. :--i. Griffey. T.

REFERENCES CITED

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B1aga. ;\. and Y:lrna:iaki. R. S .. 19i3: \lecha- ni:im 01' :iurrace microcracking or matrix in glass-reinrorced polvester b~ artilicial weathering.jrJ/lmaloj'.\/fllmai'\Sdma.8: 1331-1339.

Bmckie. W.J .. 19i'2: Expaimental rrost shatter- ing. P"n""dint:,_,~t'th" 51h'v':lt'Z"a/arld C""t:raphioz!

COflt:"'.I'I. Iii-185.

Collins. A. R .. I~l++: The destruction or concrete by rrost.jO/lma/ o(lh" Irotill/l" 0(Ciill! E"!!i""",,.

'23: '29-+ 1.

Connell. D. and Tombs.J .. 19i1:Thecrvstalliza- tion pressure or ice - a simple experimenr..1^{0 ,,'-}

"a/"fC/ano/,,!!;·. 11)(59): 31'2-315.

C""k. F ..-\. and R:liche. ". G .. 1902: Freeze-thaw C\'Cles at Resolute. :\.\\·.T. C"o!!fflph!"a/B"II"li".

:'-10 18: o+-ifl.

Dunn . .-\. and Hudec. P. P 196fi: Water. cI:lV and mck suundness. Ohio ;""rna/"IS"i"'I('·. ri6:

153-108

Fr:lser .

.J.

K .. 1'.159: Freeze-thaw rrequency and rnechanlGd \\'eJ.thering in Canada. :1'''11<'. I')' .+f).jj

French. H. \1.. !07f:i: Ti" P'fI-.:/ac:,,/ l:"c·((""!I"'''I.

L<l,ul<lll: Lon\5mJ.n.'l1)9 pp.

fllkad:l. \1.. 1'J71: Fr~ezing-thawin'.i pmcess "I' water in por~ ;pace or rocks. L"rt: '("!lWl'mlllfl' S,.i('1/o·. Ser ..-\. 29: '225-2'29. . ___ . 197'2: Fret:zini·~h~\Vin'.{ process Ill'W:iter

Meadows. H. ElIiott. :V!. Hambrev. and B.

Whalley. Dr. Colin Thorn kindlv re:td. com- mented on. and improved the original manuscript and provided much stimulating discussion on nivation processes. Dr. Sidnev \"'hite and an anonymous reviewer made man\' \'alu- able comments on the original manuscript.

The manuscript w:ts written while the author was glacial geologist with the South ;\frican Subantarctic :Vlarion bland Programme.

in por~ space of rocks. 11. Low TI'I"pa"Ulf".)·,.i- ma.Ser . .-\.30: 183-189.

Gardner.,} .. 19fi9: Snowpatches: their inlluence

<In mountain wall temperJ.tures and their geo- morphic implications. C'f'!!'a/iska .4nnail'f. )1.-\:

11+-1 '20.

Grawe. O. R .. 1936: Ice as an agent of rock weathering: a discussion.joumal

4

C"olo~l'. ++:

1n-182

Hall. K. J .. 19i5: :"ivJ.cion processes ac J late- l~int;. north-racing snowpatch site in .-\uscre Okscindbredalen. Okstindan. northern :"<lr- way. \I.Phil. thesis. (;ni\'l:rsity of ReJ.dim;.

30i pp.

Harri:i. C .. 1972: Processes 01' soil mO\'ement in turr-banked solilluctioll lobes. OkstlnuJ.n.

northern :"orwav. f" PI'ice. R. J. J.nd Su,;den.

D. E. (compilers). P"/a'C,!omo'.bi/rl/o!f,)'. Institute or British Geol.{raphers Special Publiotion -t.

London: Institute or Bricish Geographers. ⁱ)5- 1i+

- - - . 19i-1-: .-\utumn. wintel' and sprin", soil telllperatures in Oksrimbn. :"orwJ.v.

i'I/l

^ff/a^I^"I'

C/""I"/"~l" U(fi9): 5'21-53+.

Hewicr. K .. l'Jtio: The freeze-thaw en\'ironment"I' che Karakorulll Hirnab"J.. C"!lar/:a" C"'·"'I.?i,('f

1·2H5-9H. . - .

Hutlec. P. P. l'li:J: Weatherin", <l1'l'Ocks in arctic .llld sUU-"rctlc L·Il\·,ronrnent. In .-\itken. J. D and GL1SS. D ..J. ^(,:(1:;.). P'''u'crh,,-.:, 0('h,' S"m- P"'/{lff'"t',h,'Canadian :In{lC. \Vaterlo,,: Geol;,gi- cd .-\:i:ioci"tion "I' C,'nada. LIliver,itv "I'

\\<tterl"".:it:J-:n.1.

K. H\1.1. I I_~):i

•

Iv,:s,.J I) .. 11I;:i: :\rTrrr ,"ld,lip"1<' c:<'ol!\orphol- ,,<;\,-,1 ["(:\'Ie'" ur currel1t 'llJliook al1d I1lll:,lJk

<;:'ps In kno'" l<:dc:e, l:r F:II1<'\', B, D, :lIld Thornpsol1, R, (eds,L R,,\,/'(/,ch ", 1'01",,,1/(1.·11- jUTlr C;,.mnnrpno!0t.:,r Pf(l«(fdi1J!!\ .lrr/ (;utlph Srm·

/)(1\/11111 ott (;"(Jmtl'pilOlo~)'. }f);.')'. :\ior\"'ich:

c.;':o:\!Jslracrs.I-IO,

L:J1r1dou, ,J,. 19; I: CllnC!USIOI1S ~ener:ll<: des ...:chnches de' <;':Ii1'r:Jc:iol1 e:-;pnirnen(al<:. COllrt·

.\·rlllll"rI!l!t\ Rich/,r,,;,,·\, Soml'IIIlIU', C·..llr/, d/' C;I'II-

!fIfJr/Jhoin!;u'rit C(J('!11311//(1:11, to: oj-79.

\brtin. R J. [11. I~;~: Time'-ckpendenr crack

;;rowlh In quartz ane! irs applicariol1 to(he creep or roc ks ..Iou mal01'C,.".~;t;'JlwlR,'\'mnh. 77: 1+06-

1+19

\Ltrllni . .-\.. 1967: Preliminar\' e:-;perimenral ';[udies or rrosr "'earherin~or certain rock (\'pes rrom (he \\'es( Sudeles. DlUlrt)'n Prr)'glac;aln)'.

11) 1+7-19+.

\kllor. \1. 19;3: \lechanic:li ;:mlperries or rocks

:.1110'"letnperJrures. h, P,.nl/{:!rrlll ..\·orlh.~I/I/'T/

(fin COlllnnIJltr111 :0 ^,ill' .)·fronrl 1'llrr~Wllfln(/1 ConJrr- ,.,,(/'. }'"J.UISA. fY;.'. v\·ashin!;'wn. D. C.' :\a- (ional.-\c:Jdem\'or Sciences.33+-3++.

POllS ..-\. S,. Ill70: Frosr :lcriol1 in rocks: sorne experimenr:J1 d:JI:J. TTI1:r.rnr!llIll,\ "1/(1PII!H'r\, ,,;'Ihr1,,-

,!lIILlI' 0/Hri/l.(h Cl'IIg'lIphrr,l.+9: 109-12+, Rilchie. T .. 1972: Freeze-lh:Jw action on brick.

.lol/Tlla/Ill'Ihr Cal/fldinn Crramir SII(irl)'. +^{I: 1-6.}

Sch:dTer. R. J. 19:;'2: T!le wealhertng or nalural buildinL; slOnes. L' i\ Drparlmml11/Srtfllliji', and l"du,aT/al NOrrJrrh. RI/i/riing Nomrrh !:>jlf'cial Nr-

!JlITI. 18. 1+9 pp.

Thumas. W, :\ .. 1938: E:-;perimenls on rhe freez- ing01'certain buildingmalerial~. CA:. f)rparl- mml 0(Scir,'II(ir 1I"r/ I"nu.rlrial RfJrarch. RI/i/r/in!;

Nl'ltnnh Ta;lTlTml Paprr. 1;. l+ii pp.

19+ .-\RCTIC .-\.'10 ALPI.'IE RESE,\RCH

Thorn. C. E .. l'i7-f: :\n :,nah-sIS<\1 nl\'alion pr,,- cesscs :'I1J Ihelr geomorphic sic;nllicance. "'i\V(){

Rid<;e. Culorado Fronr Rall(;,e. Ph.D. IheslS.

L'ni\'ersi(v uI'Colnr:ldo.3^c⁾I pp.

- - - . 1975: .-\ model of ni\'aliol1 proCl·SS(·S . .~n

no/.\ '!!^.'h,..·!SJ(}Cialwl1 n/."lmrr/cnn C,"o/,:rnpi/r·T\. 7:

'213-2+6

- - - . 1976: Quanrir:Jti\'c c\':llualinl1 of ni":llion in rhe Colorado Front Range. C,.,,/o!;,mlS<I(I(/)'

o(.~IIImca Rufle/in.87: 1169-1 178.

- - - . 1979: Bedrock freeze·tha\\' "'e:llhering regime in an Alpine en\·ironme'nt. Colorado Front Ran!;'e. EarlhSurlacePrnccS.\cJ.+:211-'228, Thorn. C. E.-and H:l11.

K. J ..

^{in press:} ~i\'alion:

an arctic-alpine comparison and re:lppraisal.

.l0l/Tllal"r Ciaciolngr.

Tricart.

J ..

1956: Eludes '::-;periment:lle du prob-

leme de la geli\'ation. BIII/rll'" P"l'!;iaclal,,)'. +:

285-318

- - - . 1970: C,.oT11orpi!%!!..J" (~,. Co/a" E!l~'ir(l"111t'T1I\".

(Translalion by E \\'alson.i L,llldon: \bc- millan. 3'20 pp.

Whire, S. E .. 1976: [5 I'ros( action really onh- hvdralionsharrerin~).-\ rc\·il'\\' .irr!ir nnd .ilp/.·", RCJtnrrh.R: 1-6.

Wiman. S .. 1963: A preliminan' SI~ld\'^01'nperi- mcnt:J1 rrost wearherinc;, CI'II!;rali(Aa .-II/I/al(,.

45A: 113-121.

"','or~lrv. P. and Harris. C .. 19~+: E\'ickncl' ror

\i,·oglaci:.ll solillllcriol1 al Okslltldan. nhrth :'-iorwav . .-1rC!lr.27: 1·28-1H.

\\'ors!e\'. P. and Ward. :VI. R .. l^Q74: Plant colo- nizalion or recent '-annual': mor;lIne ridges ;11

Auslre Okslindbreen. norrh :\or"':l\· ..-1rrll< I/nd .-1lpin/' R£'Jrarch.6: 217 -230,

processes at a nivation site in northern Norway

KEVINJ. HALL

Hall. K.J. 19K5.Some ohservations on ground temperatures and transport processes at a ni.-at",n site in northern Norway.Nonk gtogr. 1idsskr. Vo!.39.27-37.Oslo. 155:"«ll2'/·1951.

Ground tempcralUre data. at various depths. beneath and around a trans,'cnc sno"l'ateh ill a nivation site in northern Norway arc prcsentcd. This informalion h intcgratcd "'ith ob.cruliom of dehris movement. of which four main types arc idcntificd, A temporal and~tial conunuurr. of transpurt proccsses from spring to carl)' wintcr is suggcstcd, D"crall. it is hypothcsivcd that cnhan:cd transport may be characteristic of nivation Silcs.

Kt\'inJ. Hall. Gtograplly Dtpartmmt. Unil·tniry of Natal. P. O. Box 375. Pitttrmant:burg. Sowh Africa.

Introduction

Nivation is a collective term which encompasses all aspects of weathering and transport which take place within the presence of late-lying snow (Matthes 1900) and is a process which has been widely postulated as a major agent in landscape development (Tricart 1970, p. 113; French 1976, p. 12). Despite its apparent pervasion throughout past and present periglacial areas, the limited number of studies undertaken on this topic (see Thorn & Hall 1980, Table I) have been largely qualitative. The recent quantitative work on nivation (Thorn 1974, 1975, 1976, 1979a, 1979b, Thorn & Hall 1980, Hall 1975, 1980) has ques- tioned some of the basic tenets relating to the role, timing, interrelationship and results of the processes assumed to be involved.

In the context of transport within nivation, available information (Thorn & Hall, 1980, Ta- ble I) indicates that, with few exceptions, soli- f1uction and sheetwash are deemed to be the major agents. However, the interrelationship and specific timing of these two processes, cer- tainly within the Alpine context, is considered to be largely in doubt and mainly conjectural (Thorn 1979a). Whilst detailed work on mass wastage and meltwater activity within periglacial regions is extensive (see Embleton & King (1975) and Washburn (1979) for review of litera- ture), little research on these topics has been undertaken at nivation sites despite the apparent close association. Integral with the consideration of the transport processes is the investigation of ground temperatures which, again, are limited

with respect to nivation sites, Thorn (l979b) being the only major study freely available.

In this study, ground temperatures. at \'arious depths, beneath and around the snowpatch during periods of accumulation and ablation. together with observations and measurements of transport activity, are integrated to give some assess- ment of the overall process combination. The study, although lacking in detail in certain sec- tions, was an attempt to follow the temporal and spatial variations of processes and so to de\'elop a comprehensive picture of nivation transport activity.

The study area

Investigation of the conditions and proces~~ ir association with a semi-permanent snowpa:ct were undertaken on the north-facing slope 0 Austre Okstindbre valley, Okstindan. Sortb:rr Norway (Fig. 1). The study site is located ap proximately 80 km from the coast and thu~ :x periences a realtively maritime climate.E:'(tra~

lation from the nearest meteorologiC2.i stau:m Hattfjelldal (380 m a.s.I.), which is situated~':nl

55 km to the south (Worsley &. Harris ; 9-~

Worsley & Ward 1974) suggests a me", a.'1n~;]

temperature at Okstindan in the ranli!e of - :: tl - 4°C, annuai precipitation approichmg l~l) mm and a snow cover of approximate:[ \ :~

d yr-1.The mean Januarv and Jul\tem:-:r~!U:~

at Hattfjelldal were - 9:6°C and '10.6'( res~

tively (Harris 1974). but these ma\' be_10~'er<

Okstindan due to the greateraltit~de.

Dalam dokumen Mechanical weathering in cold regions with special emphasis on the Antarctic environment and the freeze-thaw mechanism in particular. (Halaman 63-82)