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Val Vannet looks at the geographical side of Mark Beaumont's journey as he reaches the final stage of Cycling the Americas...

In the last geoblog we left Mark battling through the winds of Patagonia on the last leg of his 13,000 mile journey from Anchorage in Alaska to Ushuaia in Argentina. Over the next few days, the battle with the wind continued and even got worse! Small wonder that the Argentinians have road signs depicting the wind - like this one taken by Mark and showing the side winds which drivers (and cyclists!) can expect on this road. It was so windy - buffeting gale force winds in excess of 50mph - that at times Mark was forced to get off his bike and push. Not even the relentless winds of the Nullarbor in Australia when he was cycling around the world, forced him to do that.

The people who live in this southerly part of Argentina are used to seeing the effect of the wind on any plants which push up from the shelter of the ground. The few trees which manage to grow become 'flag trees'. They develop a form which looks like a flag being blown in the wind.

Flag tree on south coast of England, identical in form to

So why is this part of South America so windy? The answer lies in the map below...

In mid latitudes (between 40 and 50 degrees N and S of the equator), the prevailing or most common winds are westerlies which come from the south west in the northern hemisphere and from the north west in the southern hemisphere. The big difference between the winds is that in the southern hemisphere there is hardly any land for them to cross. Land masses slow winds down but between 40 and 50 degrees south there is only the tapering continent of South America, the island of Tasmania and a bit of New Zealand to get in the way of the winds. The strength of the wind in these latitudes has long been known to sailors who refer to them as the 'roaring forties' - only surpassed by the 'furious fifties' and the 'shrieking sixties' which blow in the Southern Ocean closer to the Pole!

Just when it looked as if the last few hundred miles to journey's end in Ushuaia would be a sort of 'victory lap', the roaring forties threw Mark a whole set of new challenges. In addition, although Ushuaia is in Argentina, he had to go back to Chile to get there! We need another map to explain that...

Argentina 'runs out of land' at a stretch of water which separates it from Tierra del Fuego. It is called the after the Portuguese explorer who led the first circumnavigation of the globe between 1519 and 1522. His ships sailed through this strait when looking for a passage from the Atlantic to the Pacific Ocean. It was Magellan who first gave the name 'Land of Fire' to after the large number of fires which he saw burning on land and which were probably keeping the native Amerindian tribes in this inhospitable area warm!

In order to reach Tierra del Fuego, Mark was obliged to cross the Chilean border once more so that he could catch a ferry across the Magellan Strait. As the map shows, Tierra del Fuego is divided between Chile and Argentina with the border running from north to south through the island. Here it was on Tuesday that Mark crossed the border from Chile to Argentina for the second time on his journey (the first time was just before Christmas when he crossed the Andes en route to Mendoza) and here is the he cycled past.

After the flat plains of Patagonia, there was one last encounter for Mark with the mountain chain he had followed along his journey. The is the longest mountain chain on earth, stretching from Alaska in North America to the southern tip of South America coming finally to an end in Tierra del Fuego.

And here it is... The last range of the American Cordillera with the last pass to climb (or the first if you're heading north!). We can only imagine how Mark will be feeling as he freewheels down into , the most southerly city in the world.

Val Vannet

He's made it! After 268 days, 13,080 miles cycled and 2 mountains climbed, Mark has crossed the finish line. For the latest from Mark, and how he's feeling after his remarkable journey, head on over to the Cycling the Americas site.