Gruta do Lago Azul Natural Monument (Blue Lake Cave) is a natural monument in

Bonito Bonitos are a tribe of medium-sized, ray-finned predatory fish in the family Scombridae – a family it shares with the mackerel, tuna, and Spanish mackerel tribes, and also the butterfly kingfish. Also called the tribe Sardini, it consists of ...

, Mato Grosso do Sul, Brazil. It holds two caves with interesting but fragile

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

formations, and has been listed as a protected area since 1978.

Description

The Gruta do Lago Azul has a main hall with a floor that slopes to a subterranean lake over long. The entrance is circular, about in diameter, illuminating the lake with sunshine. Between the months of September and February the waters take on an intense blue color, for which the lake is named. Fossil bones have been found of large mammals that inhabited the region for more than 12,000 years in the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

. These include

giant sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. The term is used to refer to all extinct sloths because of the large size of the earliest forms discovered, compared to existing tree sloths. The Carib ...

armadillo Armadillos (meaning "little armored ones" in Spanish) are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along wi ...

s and

sabre-toothed tiger ''Smilodon'' is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. Although commonly known as the saber-toothed tiger, it was not closely related ...

s. The Gruta de Nossa Senhora Aparecida does not contain water and has little natural light. It has a single, large hall with a sloping floor at its widest. The hall contains

speleothem A speleothem (; ) is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on ...

s, some of which are called "angels" since they resemble humans with wings. The Gruta de Nossa Senhora Aparecida is closed to visitors for safety reasons.

History

The Gruta do Lago Azul and the Grutas de Nossa Senhora Aparecida, both in Bonito, Mato Grosso do Sul, were listed as natural monuments in 1978 by the National Institute of Historic and Artistic Heritage (IPHAN). The objective is to preserve the very fragile calcareous structures in the cave, the lake and its aquatic ecosystem, and the landscape around the caves. Visitors are allowed, accompanied by guides from the municipality of Bonito. Regulations are designed to prevent any damage to the cave.

Notes

Sources

* {{DEFAULTSORT:Gruta do Lago Azul Natural Monument Caves of Mato Grosso do Sul Environmental protection areas of Brazil Natural monuments of Brazil 1978 establishments in Brazil