We´re still in Patagonia, but we`re back in Argentina in a town called El Calafate. The town was originally established in the 1920s as a stopping off place for farmers taking their wool across to the Atlantic coast ( about 2 months ride away ! ), but today its main claim to fame is its proximity to the Perito Moreno Glacier.
The Perito Moreno isn`t the biggest or grandest glacier in the area, but two things make it stand out. One is its accessability and the second is `The Big Ruptures` ( more of this in a moment ).
As you approach the glacier it looks just like you`d expect. A big ice sheet stretching across the lake. It`s only when you get closer that you again start to see the huge fissures and crevices that litter its surface. Also, when you get close, you start to hear the creaks and groans coming from the ice. Everynow and again chunks fall off the snout into the water - sounds like a rifle going off, followed by a clattering and then a splash. Really fascinating to watch.
To give you some idea of scale, the snout is about 150 tall ( about 50m above water and 100 below ). The ice in the centre of the snout takes about 200 years to get there from being a snowflake in the mountain top, whilst the at the edges, the process takes about 400 years. Boundary layers in action !
Later on in the day, we wandered down to the lake front. The whole beach area is littered with icebergs and berglets. Very pretty. You can`t really get bored of scenery like this.
Anyway, what´s `The Big Rupture´I hear you ask .. . . The Lago Argentina, that the glacier flows into, is roughly in a C shape. The glacier flows into the bulge of the C from left to right, just where a peninsular juts out from right to left. The glacier advances at about 1m per day so if it puts a bit of a spurt on, it can bridge across to the peninsular and effectively create an ice dam that splits the lake into two halves. Once this happens, one side of the lake tends to fill up with melt water more quickly, so the water level can be up to 8m different ( it`s about 2m different at the moment ). This volume of water pressing on the ice dam takes its toll and eventually the water will tunnel under the dam and rupture it. The event is hugely spectacular as the ice wall shatters and millions of tonnes of water cascade through the gap. The last time this happened was about 3 years ago. Who knows how long the current dam will last ? Could be anything from another year to another twenty.
Here´s a sweep of the glacier, with me wibbling on about the ice dam etc etc ( bit overexposed I`m afraid- the camera doesn`t like video of glaciers it would seem ) .