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In the last 'Cycling the Americas' posting on the Learning Blog, we learned about the lengths Mark Beaumont is going to as he cycles over 10,000 miles and across 110 degrees of latitude on his journey from Alaska to Argentina. In this posting we will learn about the heights he is going to as well.

Most people who wanted to cycle from the far north of North America to the southern tip of South America would look at a physical map like the one above and choose a route which kept to the lowest and flattest ground. Mark, however, is not like 'most people' and when he looked at the map, he saw that the mountains of North and South America (the Western Cordillera and the Andes) marked out an almost continuous line of brown - a ready made route running all the way from Alaska to Argentina. So in May of this year he set off on his bike to follow that line of mountains and along the way to climb the highest peaks in North and South America - Mount McKinley in Alaska and Aconcagua in Argentina.

If you want to look more closely at the route he has been following, there is a very good interactive map over on the Cycling the Americas blog where you can switch between the road map and a satellite map and zoom in to see how mountainous most of the route has been.

The line of mountains along the western edges of north and south America are fold mountain ranges formed when the edges of the earth's crustal plates have been crumpled by collision.

The map above shows the main plates of the earth's crust and you can see that there are major plate boundaries which follow the western coasts of North and South America. When plates are moving together, as they are off the western coast of South America, one plate dips below the other causing crumpling at the edges. Mountains which are created this way are said to be folded. The word 'cordillera' comes from the Spanish word for rope and it describes their twisted and buckled rocks very well. Geologically these mountains are 'young' because they are still in the process of being formed. They also tend to be amongst the world's highest mountains because there has not been much time for them to be eroded away. Back in June Mark climbed Mt McKinley which, at 6194 metres is the highest peak in North America. In January he hopes to climb Aconcagua, the highest mountain in South America. At 6962m it is also the highest peak in the world outside Asia.

It is worth remembering that mountains are not just hard work to climb, they are also very cold work! Every time you climb 1000m, the temperature drops by around 6°C. This drop in temperature with altitude is called the lapse rate and it is the same all over the world. That is why on a winter's day in Aviemore, when the temperature is 6 degrees, you can expect it to be snowing on the 1000m high mountain tops of the Cairngorms. Imagine then how cold it must have been for Mark when he was climbing Mt McKinley (6194m) back in June. If the temperature at the foot of the mountain was about 12 degrees, how cold was it on the summit? (Answer at the end of the posting).

A combination of high latitude and high altitude make Mount McKinley one of the coldest mountains in the world. In November 2003 a North American record low temperature of minus 83°C was recorded on its summit. Mt Everest may be higher but it is much nearer the equator and so isn't as cold. Here is one of Mark's photos of Mt McKinley taken when he was flying in to base camp on the mountain. The glaciers flowing off the mountain are one indication of how cold it is.

The mountains which line the western sides of North and South America are not all as high as Mt McKinley and Aconcagua but most of Mark's route has been in mountainous terrain and he has had lots of ups and downs! One of the interesting 'ups' in North America was which he did several times. The photos show Mark at an information board when he crossed the divide for the first time in northern Canada and then later on his journey when he crossed it again in the south of USA. Mark is no stranger to the continental divide in America, having crossed it two years ago when he was cycling around the world. You can .

Earlier in this posting we learned that the mountains which form the route of Mark's journey are fold mountains created by the buckling of the earth's crust where crustal plates meet. However, that is not all these mountains have in common. Many of them are volcanic and are also earthquake zones! The west coasts of north and south America are part of the 'Pacific Ring of Fire' - an almost complete ring of earthquake and volcanic regions which surround the Pacific Ocean.

When plates converge and one is forced to dip down beneath the other, friction builds up which may be released suddenly causing an earthquake. The crust may also crack under pressure allowing molten magma from within the crust to rise to the surface and form volcanoes. If you look at Mark's route and compare it with the Pacific Ring of Fire, it is no surprise that Mark has seen many volcanoes on his journey. Here, for example, is the almost perfect cone of in Nicaragua.

At the beginning of December, Mark cycled through Pisco in Peru where a massive earthquake in 2007 caused hundreds of deaths and much devastation. . It would also be interesting to look at these and then to read what Mark has to say about how the region is recovering two years after the earthquake.

The last 'Cycling the Americas' posting on the Learning Blog was called 'This time with latitude'. Perhaps this one should be 'and this time with altitude'? As we have seen, the mountains are providing many of the 'high'lights of the journey.

Val Vannet

P.S. It was minus 24°C on top of Mt McKinley!