The existence of a glacier is a balancing act between competing forces: snowfall at the névé, high in the mountains, battles with rapid melting at the terminal lower down the valley, the victor determining whether the glacier will advance or retreat. Snowfall, metres thick, gradually compacts to form clear blue ice, accumulating until it starts to flow downhill under its own weight. Friction against the valley walls slows the sides while ice in the centre slips down the valley, giving the characteristic scalloped effect on the surface, which is especially pronounced on such vigorous glaciers as Franz Josef and Fox. Where a riverbed steepens, the river forms a rapid: under similar conditions, glaciers break up into an icefall, full of towering blocks of ice known as seracs, separated by crevasses.

Visitors familiar with grubby glaciers in the European Alps or American Rockies will expect the surface to be mottled with rock debris which has fallen off the valley walls onto the surface; however, the glaciers here descend so steeply that the cover doesn’t have time to build up and they remain pristine. Rock still gets carried down with the glacier though, and when the glacier retreats, this is deposited as terminal moraine. Occasionally retreating glaciers leave behind huge chunks of ice which, on melting, form kettle lakes.

The most telling evidence of past glacial movements is the location of the trim line on the valley wall, caused by the glacier stripping away all vegetation. At Fox and Franz Josef, the advance associated with the Little Ice Age around 1750 left a very visible trim line high up the valley wall, separating mature rata from scrub.

Book through Rough Guides’ trusted travel partners

New Zealand features

The latest articles, galleries, quizzes and videos.

A postcard from New Zealand: where Maori culture is making waves

A postcard from New Zealand: where Maori culture is making waves

Despite centuries of colonialism that have had a devastating effect on the traditional indigenous way of life, Maori culture in New Zealand is experiencing a re…

26 Mar 2018 • Rachel Mills local_activity Special feature
Quiz: where should you go for an adventure in New Zealand?

Quiz: where should you go for an adventure in New Zealand?

With spectacular mountains, incredible lakes and sprawling national parks, New Zealand makes for the adventure of a lifetime. The locals call it “Godzone” (…

15 Dec 2017 • Aimee White help Quiz
Everything you need to know about backpacking New Zealand

Everything you need to know about backpacking New Zealand

New Zealand’s craggy coastline and beautiful national parks beg to be explored. The scenery gets more spectacular around every corner, with beaches, vineyards…

21 Nov 2017 • Rachel Mills insert_drive_file Article
View more featureschevron_right

Privacy Preference Center

Necessary

Mandatory - can not be deselected. Necessary cookies help make a website usable by enabling basic functions like page navigation and access to secure areas of the website. The website cannot function properly without these cookies.

PHPSESSID,aelia_cs_selected_currency,cookie_notice_accepted,RS,bp-message,bp-message-type,id,UIDR,w3tc_logged_out,__cfduid
__cfduid

Statistics

Statistic cookies help website owners to understand how visitors interact with websites by collecting and reporting information anonymously.

__utma,__utmb,__utmc,__utmz,_ga,_gid,__atssc,__atuvc,__atuvs,di,dt,ssc,ssh,sshs,uid,uit,xt
__utma,__utmb,__utmc,__utmz,_ga,_gid
__atssc,__atuvc,__atuvs,di,dt,ssc,ssh,sshs,uid,uit,xtc

Marketing

Marketing cookies are used to track visitors across websites. The intention is to display ads that are relevant and engaging for the individual user and thereby more valuable for publishers and third party advertisers.

__gads,PISID, BEAT, CheckConnection TempCookie703, GALX, GAPS, GoogleAccountsLocale_session, HSID, LSID, LSOSID, NID, PREF, RMME, S, SAPISID, SID, SSID,__utmv, _twitter_sess, auth_token, auth_token_session, external_referer, guest_id, k, lang, original_referer, remember_checked, secure_session, twid, twll,c_user, datr, fr, highContrast, locale, lu, reg_ext_ref, reg_fb_gate, reg_fb_ref, s, wd, xs
__gads,PISID, BEAT, CheckConnection TempCookie703, GALX, GAPS, GoogleAccountsLocale_session, HSID, LSID, LSOSID, NID, PREF, RMME, S, SAPISID, SID, SSID
__utmv, _twitter_sess, auth_token, auth_token_session, external_referer, guest_id, k, lang, original_referer, remember_checked, secure_session, twid, twll
c_user, datr, fr, highContrast, locale, lu, reg_ext_ref, reg_fb_gate, reg_fb_ref, s, wd, xs