"MOUNTAINS AND RIVERS."

Otago Witness, Issue 2727, 20 June 1906, Page 12

"MOUNTAINS AND RIVERS."

LECTURE BY DR P. MARSHALL. There was an attendance of about 40, of whom eight were men and the rest women, at Thur&day night's meeting of the Froebel Club, in the \'.W.(J.A. Hall, when Dr P. Marshall was the lecturer. Tlie chair was occupied by Dr Colquhoun. Dr Marshall delivered a most interesting and instructive lecture _on " Mountains . - and Rivers " from the_ viewpoint of their effect on fhe structure of the earth, with special reference, of coarse, to New Zea- ' land, and the South Island in particular. ! He' dealt at the outset with volcanic action, and instanced Egcmont as one of -. ' the best instances of complete volcanic growth, where the building up had been gradual and continuous right to the finish, giving 1 the beautifully symmetrical appearance that was the great charm ( of Taranaki's mountain. In contradistinction to this Ruapc-hu, no great distance away from it, was cited as an instance where the volcanic action, instead of gradually simmering out and leavinpr the cone in- } tact, as in the case of Egmont. had culminated in a final gigantic throw, givinga broken and rugged top. Lyttelton Harbour was another result of the same kind of action. Dunedin was a volcanio district, but so much older that the destructive forces of streams had prevailed for so long a time that it was now hard to say where the actual cone oe actual crater was situated from which the vast amount of rock on Mount Cargill. Flagstaff, and Otago Peninsula was deposited. Volcanic action, however, was spasmodic, and was an insignificant factor in earth structure. • A single throe-days' flood in the Water of Leith" in September of last year removed no less rhan 45,000 tons of material' from Flagstaff and Mount Caririll and deposited it in the harbour. That being so, what an enormous amount of material must be , deposited in the basins of the sea about New. Zealand in 12 months, and how much greater that quantity of material must be than the relatively trmall amount deposited by the Tarawera volcanic eruption in 1886. , Coming to the mountain i-anges of the South Island, which formed such a j characteristic feature of New Zealand's coast when seen from a distance, the lee- ! turer mentioned in passing that some of ! the glaciers on the Southern Alps attained j a size hardly equalled anywhere outside ! of the Arctic nr Antarctic regions. Those great mountains, solid as they seemed, ' wero anything but permanent, and were constantly being rent asunder by frosts and running water and the material was being spread on the plains. Our mountains were the constant renovators of the fertile plains of rhe country. The ice of which glaciers wer» formed was not a hard substance in reality, but \va?- of a gluey nature, and flowed, sluggishly it wa.s true, but it flowed, and the glaciers were really ice rivers. Within comparatively recent geological times g-laciors in New Zealand .had flowed right on to the plains, and even to the '<ea coast. This was appa- , renr in Canterbury, rvnrl also south of Dunedin where tho Taieri flowed through irs final gorare to Ihe s->a. The sides of that gorge shaived that it was =in-.plv the remains of the hupe quantity oi debris which always formed the toWnr cf a glacier, and was cons(amlv pushed on in front ot it until, the climate chp.njring-. tho jrlacier melted and lefr this solid deposit. The glaciers of rhe So-jphrrr) Alps wrc all mo vine, the Tasnia:i at tho rate of one ; foot per day to the Franz .T o -eph .it the ! rnto of 10ft per clny rhe '"isteM oi tho I Now Zealand srlaci3Ts. TV"? surin<--es of ' th^se glaciers were coverc! with hillocks pn r \ crovicos. and through the crevice* . rocks ami stones wer« continnaUy falling and forniins norr of tii^ hoc l of •'-, > j jrla'-'-or. As the jrr"ii n as' i^ov. .1 onv s ] } ;hese •>*or" i s our thfii wavintc*J"» n>iternl ; o^er which rhc \» a - rimin-r. mi'] ', j to this act^n wp ~ st'< ribirr-iMi'. in •'•■» ' opinicn of Dr Mar-Ji^.i! ;'•"> ,;j;c*>«H lak» i sco»?rv ;\-h.]"h -'as "o o-'t. .»-— , ,-" •> ff:'a-»f f:'a-» of Ota-2 I^ko TTai.'"r;.u La'?« A^rV- \ pna-i, i.-.l La .-> Te .\r.^! «• -a c- -t-lo< ,'•<} , ; illaoti'ai-icns pi «u.i rh.^ \r-r\ 1----I i ill-i '•rx.Hon of ail ''"i'n.cn V ..l : -. .it | ih- l^rd .' Jy. u f; Te Ai ia -. X— ' ir->- , n<i'i a ' i I''-. -\- ••' \ .i ii -"■'' r, -i -re - --p R*Ti_--,-> !h' itrii ,i t-r-'irni (-~rn- p -m !'V , - ( -, , f> r - L * - r>) ■ r' >■* . \ pp; li-iii f»p*-.-"f »p*-.-" -w — -)-• - ,'».,-■... •r-^,] r^ ;- o t'> T •'. <■ « '„,,. „,i T ." • M .-i-.r;n ;r'- - «.. i:- -•• r, • -v, .„.,-.. o" .!— f or--,- „,. • ''' I- •-„.-..■ I n f „. . ,- , -r-- • , -• ;• r,, ftQO:c Ljlov. >.ra ic-.ci. Iho c-I'f^c c." c

streams and rivers was very great indeed • on the formation of the country. The Leith, which he had mentioned, vra^ no exception to the general effect, and that being so, it would appear that the earth must be gradually wearing away, and as a matter of fact calculations showed that the surface of the earth by this very action was being reduced in " level to tho extent of one foot in rather less than 6000 years, i There was no doubt, however, that the earth was geologically old enough to have been worn down to sea level by this time by the river action, and therefore some counterbalancing factor had to be ascertained by which mountains were at, at any rate, a greater rate than the rivers and streams tended to lower the earth's surface. Geologists believed that this was found in tho fact that the earth was cooling. They believed, that the earth was onco molten, and was gradually cooling, and if so it must be getting gradually smaller. The lecturer used the illustration of an apple, which, when picked in the autumn, filled its skin wiith v complete tenseness, but, when kept, in time portion evaporated and the skin became wrinkled. . The skin of the apple was comparable to some extent with the orust of the earth. . As the interior became cooler the surface became crumpled, and these crumples, ' which in formation were minutely gradual, . became in time the mountain i*anges. This ; wrinkling of tho surface was going on all over the earth at the present time. During this gradual wrinkling of tha cruet of the earth it was very evident that from time to time stress would arise in the solid ropk, and when that strain reached a certain stress the rock would crack. The offect of that was to produce an earfchnuake. an«-l such was probably the cause of the late rlipostrouff earthquake at San Francisco, and also of the pneat earthquake at Wellington in.. 1855. That latter earthquake, the lecturer incidentally mentioned, was of some considerable importance; in as muehy as it, l<*ft the bottom- of Wellington " Harbour 6ft higher than it was previously. ' Rovertinsr to the wrinkling- of the surface of th** earth through the interior cooling, Dr Marshall went on to say that wh^re . this gra'lual process was going on the : streams were generally able to wear their way through, and to this fact was to be attributed many of our srorges. Rofe- i rence was made to the Manawatu River, which flowed through +he backbone range of mnnnair.s of the NortTi Island, and , carried the (?raina2fe of the east sirio to its point of riisrharare on the West Coast, i The wrinkling of the surface in th*t. plnoe . ha^ reached the height of the Rnahine and Tarawora Ranges. If that wrinklinc j was formed subsequent to the outlining of the course of the Mana"wa(-u. then it was , imaginable that the river had cut its way f flown moro rapidly than the elevation of tho range har' taken nlac*. As to the for"in.tion of the beds of the Canterbury Rivers. h« favoured the theory th.^t they were the re«iul<- of jrlncier »Hion. Cominsr to +he. Olutha River, he «aid thnt this had l'ncier-rone most extraordinary vicissitudes. J The faci that thia Hvev carried away the wafer* of 'L»ke Wakntiou was only ex- j plninnb'-" by *-hn sT'onosiron that t-V>o elaoienwhich C'-unied "'hat is now the lake had an ov'flTw at Fran'-'^on ; and that when ' the dimtji' chancre! and th" grlaeier j f-'llpH *-fc« """—inkto-i outlet was aWf ro <?*»t ■f-t-TO'-^h 'nierronin" fotiwip of lane' in t'n^ rivpr whereas at f^e Kinsrston err?, ■"•Moh. *>f "onrpe. v.-f? the nati»-"a.l outlet, j b"ip<r i ! > ' > 'over <»r"1 nf f}^r» "!(ifi°r. the "•r>v r-" th^ ".-ate- hf-} hppy> 'oloc'-p'' by the }inpr-* '•mo-i'-f- of <:ol : '' matte vh'^h the "■'acie" hi" Vp^ f>niT-in-jal! T * r»'"or)e T H«o' - n ir= vji TjiUr TT *->V.T-!r)i> in th'» irr!'"arv t^o n r rrpntt .'^ti'<-I but, for *h'!> h^ve ili"ii-/»d ■'n<n *^c ~\*->i"-"-r "rtri Ore><"i. in- ' rr "-'» "-nn^.i"! "-'I T--"Hnnouc ■wat'tis s»vrp.v : of iUr> rro - " l '";i'"s f-s rre""lv p rerrrovn'. , r-'-f 1 r-ot P ''-«.•-'•" t^n T'-o ??It. ir <■»"> j J r-.ir-" i- t'mi* *nrT»-pcl a ba->'k , r ' an 1 ■"«-« r f sra'--"l, • , . •.-.',, r,.,^,i ;„(.,, t- n -. r ] lavpvo s-rr'-'u- , -!!,- '-„ :! ' «rr 4-U,,-,.,.- 1 - r-<: nn :n("o: n("o ' the ' ' r . -~ o f ">'••' pn-rV- T'->o mo > 'n*-.->ir' rpnnys | -," -\"^-- V,.-,;-. n ,l »a— 'n-'-Cfl or «~ c fchlVe ,' -O-T- ''• vi-t--/»e ■•]-•-'.. — 0,-o ., O -n- Vjoi>-.5T ' J .- • ' -',- n^/^~ .-~0/J n «i;lf »nn- " i _ ..1 i ; -..':.,,. -' it P.-v'- 1 -.- •' •> vprr he^-'-sr j .., ,r 0-,.. ' - -i=- if- ?»r! Dv ■N r crrl;iil "■ ■ 1 , ••-. — " "vr-:; 1 .- '■ - "■(" Souths in . ' - ' -ilnh : =_|_s ar.d J -l.Cx- Uil^rcola-r tii.car^ for 13. "