Colonia

Colônia Crater

The Colônia crater is a recently confirmed impact structure situated in the municipality of São Paulo, Brazil. This round, bowl-shaped depression measures approximately 3.6 kilometers in diameter and is encircled by a ring of hills about 125 meters high. Its approximate coordinates are 23°52′S 46°42′W, placing it at an elevation of 770 meters above sea level.

Geology and Formation

Geologists hypothesize that the Colônia crater was formed by the impact of a meteorite approximately 200 meters in diameter. The event occurred between 1 million and 20 million years ago, impacting crystalline basement rocks that are 600 to 700 million years old. The Earth Impact Database suggests a slightly wider age range of 36 to 5 million years ago. This makes Colônia one of the youngest known impact craters in South America.

The crater is partially filled with peat, reaching a maximum depth of 275 meters. This sedimentary material has preserved a valuable record of ancient environments, with the upper 8 meters offering a detailed climate and ecological history of the last 130,000 years. The complete environmental record may extend back as far as 2.5 million years.

Seismic and other surveys indicate that beneath the peat are 50 to 65 meters of fragmented rock deposits, followed by another 50 meters of shocked or deformed basement rock. Sediment analysis suggests that a lake occupied the crater's central part until about 18,000 years ago, after which it transitioned into a swamp. The crater is drained eastward by the Vargem Grande creek, which flows into the adjacent Billings Reservoir.

The identification of Colônia as an impact crater is primarily based on its geomorphology and faulting patterns, as well as the exclusion of other geological formation mechanisms, such as karstic sinkholes (which would require carbonate rocks, absent here). As of 2011, definitive evidence such as shatter cones or shocked quartz had not been reported; their discovery would likely necessitate drilling through the sediment fill.

Location and Conservation

The Colônia crater lies within the Parelheiros region of the São Paulo metropolitan area, approximately 35 kilometers from the city center. The crater area contains remnants of the native Atlantic rainforest. Since 1989, the northern portion of the crater has been gradually encroached upon by informal housing, now forming the Vargem Grande neighborhood, which is home to an estimated 35,000 to 40,000 people.

To protect the site from further degradation, the crater has been designated a protected natural landmark, registered in 1995 by CONDEPHAAT. Its southern section was incorporated into the Capivari Monos Municipal Parkland in 1996.