Melting Mountain Glaciers For many years it has been believed that Canada's western mountain glaciers, also known as the Cordilleran Ice Sheet, melted some 12.5 thousand years ago. A new study published in the Journal Nature by researcher Brian Menounos and his team is shedding new light on just when our mountains became ice-free. Deciphering the story of ice melt across western Canada's mountain has far-reaching implications. By understanding how ice melted thousands of years ago, we can also build better models to predict how current alpine ice sheets, like the one in Greenland, may melt in the future. It also helps to understand the challenges of previous theories of an "ice-free corridor" in terms of human migration to the North American Continent. And finally, it also is an important part of the story of ocean level fluctuations as a result of the increased meltwater. When we talk about landscapes we need to understand two concepts, inheritance and consistency. When we look at changing climates over the millennia, we also need to look at the associate landforms that each climate typically creates. In the mountain west, for instance, the mountain landscape was first carved by the power of water. Water dissects the land in a very specific way. It takes advantage of the contours as well as weaknesses in the rocks to guide its flow. Water passes over rocks of varying hardness including soft shales and harder limestones. Softer rocks will be worn down more quickly while harder rocks remain more resistant to the power of water. Cracks or fissures will be widened and over time, the landscape begins to be divided by mountain summits and intervening v-shaped valleys carved by water. When glaciers later inherited this water forged landscape, they inherited the same valleys previously carved by water and began to renovate them. Narrow V-shaped valleys were renovated into broad u-shaped valleys typical of valley glaciers. High on the mountains, glaciers also formed on cliff ledges and any area where snow could accumulate. As these glaciers moved, they enlarged the ledges upon which they sat and in many cases created round bowl-shaped depressions called cirques. I often refer to cirques as glacial nurseries as the ice usually formed there and then would overflow down the valley as it exceeded the ability of these bowls to contain the ever-increasing volumes of ice. Rock and debris fell onto the ice and some hitched a ride, just like a modern-day conveyor belt. It would later be deposited along the ice margins in linear ridges called moraines. Most of the rock becomes incorporated into the glacier and gets scraped and scoured along the base of the glacier. It's this action that allows glaciers to modify the landscape. Today, water has re-inherited this ice-modified mountainscape and is once again altering the cirques and u-shaped valleys. Consistency refers to the simple fact that processes acting on the landscape within a particular climate are the same processes that acted on the landscape at other periods of similar temperature and moisture. The way water changes the mountains today is the same way it would have done thousands or even millions of years ago. Each climate creates its own types of landforms but is always working with vistas carved by successive climatic periods. As a naturalist, this is what I love to look for in the surrounding peaks. Where can I find the impacts of previous climates and how are the current changes in climate affecting how water will shape the mountains long into the future. Brian Menounos' study helps climatologists to not only more accurately understand how our mountain glaciers melted, but also how similar landscapes today may react in the future. Just like looking at a star in the sky represents light that may have traveled for thousands or millions of years before it reached your eye, our mounta