Athropolis HOME   |   Maps   |   Arctic Links   |   Arctic Library
Click to go HOME
From our library of things you should know about the Arctic


A Blocky Pattern of Ridges

Permafrost soils (soil that remains frozen for at least two years) of the Arctic tundra are covered with an "active layer" - a thin layer of soil that thaws when the summer sun warms the tundra surface.

Sometimes ice wedges form "polygons" - a honeycomb of ice walls beneath the soil surface. These can be about 70 feet / 20 meters across, although polygons may be as small as 10 feet / 3 meters across.

How does this happen?

  • In the winter the cold causes the frozen soil to shrink, and cracks form.
  • In the spring, the active layer melts and water seeps down into the cracks. It freezes and expands when it is chilled by the still-frozen soil. The frozen water forms wedges of ice in the soil.
  • The active layer and the tops of the ice wedges melt in the summer, adding more water.
  • Each winter, cracks form again in the same places, and in the spring, more water enters and enlarges the ice wedges as the freezing water expands.
  • This cycle of crack, melt, and freeze enlarges the wedges year by year until the soil above them is pushed up, forming a blocky pattern of ridges on the ground called polygons.
MORE...
Click pictures for more information and credits.
Library: Pingos, Thaw Lakes, Wetlands
Arctic, Land, Environment/Atmosphere
Links: Arctic, Environment
Arctic Maps & Weather Reports

Double-click any unlinked word DICTIONARY: Just "double-click" any unlinked word on this page for the definition from Merriam-Webster's Student Electronic Dictionary at Word Central.
Arctic Library ARCTIC LIBRARY & GLOSSARY: Check this section for an index of the rest of the things you really need to know about the Arctic.
All sorts of Arctic Maps ARCTIC MAPS & WEATHER REPORTS: Maps of the Northwest Passage, explorers' routes, iceberg sources, Nunavut, the Arctic by treeline, temperature...
Links to related sites. ARCTIC LINKS: Even more information! Links to sites related to the Arctic and "Iceberg: the Story of the Throps and the Squallhoots".
A Guide to Arctic Sunrise and Sunset GUIDE TO ARCTIC SUNRISE & SUNSET: How much sunlight or darkness is there in the Arctic on each day of the year?

Search for more on this topic...from Athropolis!
(1) Click the button for Web (below) to search the World Wide Web
(2) Click button for
WWW.ATHROPOLIS.COM to search this web site

 
Web WWW.ATHROPOLIS.COM
Icy Cold Jokes | Icy Games | E-mail | Athropolis HOME
Copyright © 2005 Athropolis Productions Limited. The content of web sites that this site has links
to is the property of their respective owners, and Athropolis is not responsible for their content.