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The last time Mark Beaumont went on a very long cycle ride, he cycled around the world in 194 days. Starting and finishing in Paris, Mark cycled over 18,000 miles through 20 countries and across 4 continents on his way to breaking the Guinness Record for solo cycling around the world.

The world is a sphere - a circle in 3 dimensions and so like all circles it can be measured in degrees. When Mark cycled around the world, he cycled through 360 degrees and crossed many lines of longitude.

Lines of longitude are the imaginary lines on a map which stretch from the North Pole to the South Pole. Places on the same line of longitude don't have much in common other than the time of day! For example, Edinburgh is on the same line of longitude as Timbuktu in the Sahara Desert. These two places couldn't be more different BUT they are in the same time zone. When it's noon in Edinburgh, it's also noon in Timbuktu.

In May of this year Mark set off on a new cycling adventure called Cycling the Americas and this time he's doing it with latitude! Starting in Anchorage, Alaska and finishing at Ushuaia in Patagonia, Argentina, Mark is heading in a southerly direction though 13 countries, 2 continents and crossing lots of lines of latitude along the way. You can see his route in more detail and track his progress to date.

The most important line of latitude is the Equator and it divides the globe into two half spheres or 'hemispheres'. Mark began his journey in the Northern Hemisphere and will finish it in the Southern Hemisphere. In fact, he crossed the Equator in Ecuador in early November so he is now already in the Southern Hemisphere.

In each hemisphere there are 90 degrees of latitude between the Equator and the Pole making a total of 180 degrees between the North and South Poles. Mark started his journey at 62 degrees north of the Equator and will finish at 55 degrees south. In other words, he will be travelling roughly similar distances on either side of the Equator.

This is important because unlike lines of longitude, places on the same line of latitude do tend to have a lot in common - especially as far as their climate is concerned. Take, for example, Bournemouth on the south coast of England. It is located at 50 degrees north. In July, the average temperature is 18C and in January the average temperature is 5C. Compare this with Vancouver in Canada, also at 50 degrees north. In Vancouver the July average is 17.5C while the January average is 4C. It is no coincidence that they have similar climates as they are both on the same line of latitude.

Not only do places on the same line of latitude within one hemisphere have similar climates but if you go to the same latitude in the opposite hemisphere, you will find a mirror image. At 20 degrees north of the Equator Mark was cycling through the deserts of Mexico and at 20 degrees south of the Equator in Peru, Mark is in desert country again. Way back in May and June when Mark was at 60 degrees north in an Alaskan summer the weather was cool and wet. This is exactly what he can expect in February when he gets to 55 degrees south in Ushuaia when it will be summer in Patagonia (remember that the seasons are the other way round in the Southern Hemisphere!).

So, as Mark cycles south from Alaska to Argentina he is crossing many lines of latitude. As he is finding out, that means lots of different climate zones. Here are just a few of the climate contrasts he has seen so far...

Start of the journey in Alaska - cool and wet. It could be Scotland!

Coniferous trees stretch to the horizon in the Yukon region of northern Canada

Hot and dry here in southern USA

Into the tropics in southern Mexico and it's hot and humid

Wet, wet, wet in Costa Rica

Back to desert in Peru

The 117 degrees of latitude between Anchorage and Ushuaia will offer a lot of climatic contrasts but Mark's journey is not just about the distance between 62 degrees north and 55 degrees south. It is a journey about altitude as well as latitude.

In the next Cycling the Americas posting on the Learning Blog, we will look at the heights Mark has to go to on this journey...

Val Vannet