3 lava domes occupy the elongated, N-S-trending glaciated summit region, which has 2 main peaks. Lava flows less than 10,000 years old fill valleys SW and SE of Santa Isabel, but there are no known historic eruptions.
A small lava dome is found about 10 km SW of the volcano.
Laguna Verde in Los Nevados National Park is a 900x400m volcanic lake at an elevation of 4300 m 2 km NE of Santa Isabel Volcano.
The lake is known for its ecosystem and birdlife. It belongs to the Subalpine Rain Páramo, with a climate of low temperatures (3º - 6°C), annual rainfall of 1000–1500 mm, high humidity and strong winds.
In 2000, many birds were killed at the lake, because of an increase of toxic ammonium salts.
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Source: Juan C. Verhelst (2006) "APPARENT NATURAL POISONING OF NEOTROPICAL MIGRATORY BIRDS AT LAGUNA VERDE, COLOMBIA", Ornitología Colombiana No 4 (2006): 70-72
