Retreat of glaciers since 1850 doing so due to transient local weather conditions, which have brought more precipitation and cloudier, cooler summers since 2002. Tropical glaciers are located between the Tropic of Cancer and the Tropic of Capricorn, in the region that lies 23° 26′ 22″ north or south of the equator. Strictly, a tropical glacier is located within the astronomical tropics; the area where the annual temperature variation is less than the daily variation, and is within the oscillation area of the Intertropical Convergence Zone. Tropical glaciers are the most uncommon of all glaciers for a variety of reasons. Firstly, the regions are the
Bowerchalke the equator, the latitude of present-day Argentina. 'Proto-Bowerchalke' and the rest of England and Wales are part of Avalonia, a micro-continent that broke away from the southern landmass, and was 50 degrees south of the equator about 500 mya. It joined with Baltica just south of the equator 400 mya, and was crushed between Baltica, and Laurasia (North America), and Gondwanaland (Africa, Australia, Antarctica and South America) 350 mya whilst near the equator (Variscan orogeny). Avalonia was landlocked and buffeted within Pangaea just north of the equator 270 mya, and became part of a desert in the northern tropics 230