Rivers of ice have always fascinated me. Ice ages have been greatly influenced by Earth’s climate over the past three billion years, if not longer. Various theories suggest that processes such as tectonic uplift and rock weathering, sunspot activity and orbital variations have all impacted on climatic conditions and glaciations. Despite the threats of global warming, we are still in a glacial period – the icecaps in Antarctica and Greenland show us this.
A significant component of the Earth and Space curriculum addresses the understanding of climate and weather, the most recent controversies being that of climate change. Recently Tim Flannery, a professor at Macquarie University and Chief Commissioner of the Climate Commission in Australia has spoken at the Regent Theatre in Dunedin on his latest research and thoughts. Professor Flannery was named Australian of the Year in 2007, and has spoken and written books related to climate change. It is widely accepted that human activity is accelerating the pace in which the environment can adapt, environmental consequences that may frighten us in years to come. He has had some interesting concepts in recent years – initially supporting nuclear power and then opposing the idea in Australia. He also suggested the release of more sulphur into the atmosphere to block the effect of solar energy and to enhance global dimming. With global warming expected to occur in the future, glaciers will continue to melt and sea levels rise.
So what is weathering? It is the break down of exposed rocks that are transported as smaller fragments of rock and minerals. Gravity, wind, ice and water are various ways that rock is transported depending on how big the particles are and how strong the erosional force is. There are different ways in which rocks can be weathered. Biological weathering involves the breakdown of rock due to an organism’s activity, such as bacteria, worms burrowing or growth of tree roots. Physical weathering is the most common for glaciers and generally involves water and changing temperatures. Freeze thaw action will eventually spilt rocks as the water freezes and then thaws in cracks. Rocks are a mixture of different minerals, which also expand and contract to varying degrees when they warm up and cool down.
Chemical weathering occurs largely through acid rain. All rainwater is slightly acidic, as carbon dioxide from the atmosphere has been dissolved into the water droplets. However pollutant gases also dissolve in raindrops further intensifying the acidic levels. Acid rain has a significant effect on marble, which is essential limestone metamorphosed. India’s Taj Mahal in India built during the 1600’s is being significantly damaged by acid rain and has now lost is brilliant white lustre. The Acropolis in Athens was built further back in time over 400 years BC. However heavy vehicle emissions and pollutants from a congested city has contributed to the acid rain in the region. Even low levels of acid rain are having an impact on the marble surface and degradation.
Glacial Erosion, Chile and Argentina
Reaching to high altitudes involves colder climates and seeing a landscape of snow and ice. I’ve had my fair share of fun and challenges climbing through the Himalayas and volcanoes in Africa, Chile and Iceland. Glaciers are referred to as icy rivers. They flow very slowly, on average around two metres a day from the ice caps. With the tonnes of weight of ice, glaciers carve out U shape valleys with steep slides and flat valley bottoms. Moraine of rocks accumulates to the side and at the end (snout) of glaciers. Many glaciers end in oceans or lakes, as I saw in Chile and Argentina.
Perito Moreno Glacier in Los Glaciares National Park, Argentina is around 30km in length and is fed by the Southern Patagonian Ice Field located in the Andes. It was magical to see continuous ice breaking away from the glacier and crashing into the Argentino Lake. It is easy to assume this glacier is retreating – in fact it may be slightly growing, although glaciologists often debate this.
Mount Everest Nepal
Khumbu Icefall at the head of the Khumbu Glacier not far from Everest Base Camp is deemed incredibly dangerous, almost suicidal. Particularly as the sun warms up the ice in the morning, moving large crevasses open with very little warning. I witnessed large blocks of ice crashing down – I first heard what sounded like a clap of thunder before I saw the ice and then dusting of snow settling. It’s a gruesome thought that not everybody that dies in his or her pursuit to summit Mount Everest can be recovered. I was told by my guide that bodies that die in the Khumbu Icefall are often found years later as the ice moves with gravity towards Everest Base Camp. Sherpa, which is a recent documentary illustrates the dangers of the Khumbu Glacier Icefall and the detrimental repercussions within the Sherpa community. In fact it is quite a controversy, driven by a deep respect for the mountain gods.