page_title: Ice
section_title: On land and structures
hierarchical_section_title: Ice / Natural formation / On land and structures
caption_attribution_description: English: Icy Japanese Maple (Acer sp.) branch after an ice storm; Boxborough, Massachusetts, USA.
context_page_description: Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.
  In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far away as the Oort cloud objects. Beyond the Solar System, it occurs as interstellar ice. It is abundant on Earth's surface – particularly in the polar regions and above the snow line – and, as a common form of precipitation and deposition, plays a key role in Earth's water cycle and climate. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes and aggregates from snow as glaciers, ice sheets.
  Ice molecules can exhibit eighteen or more different phases that depend on temperature and pressure. When water is cooled rapidly, up to three different types of amorphous ice can form depending on the history of its pressure and temperature. When cooled slowly correlated proton tunneling occurs below −253.15 °C giving rise to macroscopic quantum phenomena.
context_section_description: Ice on land ranges from the largest type called an "ice sheet" to smaller ice caps and ice fields to glaciers and ice streams to the snow line and snow fields.
  Aufeis is layered ice that forms in Arctic and subarctic stream valleys. Ice, frozen in the stream bed, blocks normal groundwater discharge, and causes the local water table to rise, resulting in water discharge on top of the frozen layer. This water then freezes, causing the water table to rise further and repeat the cycle. The result is a stratified ice deposit, often several meters thick.
  Freezing rain is a type of winter storm called an ice storm where rain falls and then freezes producing a glaze of ice. Ice can also form icicles, similar to stalactites in appearance, or stalagmite-like forms as water drips and re-freezes.
  The term "ice dam" has three meanings (others discussed below). On structures, an ice dam is the buildup of ice on a sloped roof which stops melt water from draining properly and can cause damage from water leaks in buildings.
caption: Ice on deciduous tree after freezing rain
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