Ablation
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Ablation is the removal or destruction of something from an object by vaporization, chipping, erosive processes, or by other means. Examples of ablative materials are described below, including spacecraft material for ascent and atmospheric reentry, ice and snow in glaciology, biological tissues in medicine and passive fire protection materials.
Ablation near the electrode in a flashtube. The high-energy electrical arc slowly erodes the glass, leaving a frosted appearance.
An Nd:YAG laser drills a hole through a block of nitrile. The intense burst of infrared radiation ablates the highly absorbing rubber, releasing an eruption of plasma.
Penitente (snow formation)
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Penitentes, or nieves penitentes, are snow formations found at high altitudes. They take the form of elongated, thin blades of hardened snow or ice, closely spaced and pointing towards the general direction of the sun.
Field of penitentes (1.5–2 metres or 5–7 feet high); upper Rio Blanco, Central Andes of Argentina
Small penitentes in the summit crater of Mount Rainier
Penitentes near the summit of the Agua Negra Pass on the border between Chile and Argentina