Accumulation
Persistent snow loses air and becomes denser, feeding the glacier.
SANTA CRUZ · ARGENTINA · 50° SOUTH
PERITO
MORENO
Ice is always moving.
01 — SOUTHERN PATAGONIAN ICEFIELD
A river
of ice
Perito Moreno Glacier flows from the Southern Patagonian Icefield towards the Brazo Rico arm of Lake Argentino. Its apparent stillness is deceptive: gravity continually carries ice from the high accumulation areas towards the terminus.
~30 kmLength
4–5 kmWidth of the ice front
1981World Heritage listing
1937Year the park was established
02 — ICE IN MOTION
Accumulation,
flow and rupture
Snow builds up at altitude, compacts into ice and moves slowly downhill. At the terminus, stresses open crevasses and release blocks of ice.
Flow
Ice deforms and moves under gravity, following the slope of the valley.
Terminus
The glacier tongue reaches the lake, where water and temperature help trigger calving.
A natural dam
During its historical cycles, contact between the ice front and the Magallanes Peninsula blocked the drainage of Brazo Rico, setting up the conditions for the ice dam to rupture.
A glacier carries ice, water and the passage of time through the landscape.
03 — A PROTECTED LANDSCAPE
Ice,
forest and steppe
Los Glaciares protects a remarkable transition from vast ice masses to southern beech forests of lenga and ñire, and on to open steppe. Huemul deer, pumas, foxes and birds of prey belong to a territory extending far beyond the viewing platforms.
04 — BEFORE YOU VISIT
Watch from
a distance
From El Calafate
Provincial Route 11 connects the town with the park’s glacier walkways.
Stay on the walkways
Calving can send waves across the lake and throw ice fragments into the air. Never leave the designated routes.
Layers for the wind
Air temperature and wind chill can change quickly. Bring warm layers and waterproof clothing.
Check with the park
Opening hours, fees and activities can change. Always check the latest official information.
07 — UNDERSTANDING GLACIER DYNAMICS
Advance, buoyancy and rupture
Perito Moreno’s historical ice-dam ruptures arose from the interaction of ice movement, channel geometry and the difference in water levels that built up when the front blocked the outlet. They followed no fixed timetable, and their past occurrence does not guarantee a future return.
Ice deforms and slides
Gravity drives the glacier down from its high accumulation areas. Ice deforms internally and may also slide over its bed, at speeds that vary across the glacier and through time.
Crevasses and seracs reveal stresses within this flow. The front may look solid, but it is the visible edge of a moving system.
When Brazo Rico is cut off
If the front meets the Magallanes Peninsula, it can restrict drainage from Brazo Rico. The growing difference in water levels increases pressure until water opens a channel or tunnel.
The resulting ice arch enlarges and eventually collapses. Each cycle depends on particular conditions; there is no sound basis for predicting an exact date in advance.
Past stability is only part of the story
A study published in 2025 documented faster thinning near the terminus between 2019 and 2024, alongside acceleration and retreat. The relative stability described over previous decades should not be presented as the glacier’s current condition or as a permanent exception to regional ice loss. Bed geometry and buoyancy help explain these changes.
Walkways and viewpoints let visitors observe without approaching the unstable ice front. Staying within authorised areas reduces exposure to calving, waves and falls.
This text has been reviewed against the institutional and scientific sources listed below.
08 — ESSENTIAL QUESTIONS
Keep
exploring
Brief answers to common questions, with links that help you understand the region further.
How often does the ice dam rupture?
Historical ruptures had no exact interval. They required a blocked outlet, a sufficient difference in water levels and a tunnel that ultimately collapsed. Recent retreat means that a repetition of this cycle cannot be assured.
Does the glacier always advance?
No. Ice flowing towards the lake does not necessarily mean the terminus is advancing: a glacier can lose mass and retreat while its ice continues to move. Research published in 2025 documented accelerated thinning and retreat. Continued measurements are needed to track its evolution.
Why must visitors stay away from the front?
Calving produces falling blocks, waves and unpredictable flying fragments. The walkways allow observation at a distance, outside the immediate impact area.