Colônia crater
Encyclopedia
The Colônia crater is a presumed impact crater
located in the municipality of São Paulo, Brazil
. It is a round bowl-shaped depression, without any obvious central bulge, with a diameter of about 3.6 km, bounded by a circular ring of hills about 125 m high relative to the inner depression. Its approximate location is 23°52′15″ South and 46°42′30″ West, 770 m above sea level. The name comes from the town district of Colônia located just North of the feature.
with a diameter of about 200 m. It was formed between 1 million to 20 million years ago, in crystalline basement rock
s 600 to 700 millions of years old. In any case, it would be one of the youngest South American impact craters known. It is partially filled by turfaceous
sediment
with maximum depth of 275 m, which provides a precious record of ancient environment. The upper 8 m, in particular, have provided a detailed climate
and ecological
record of the last 130,000 years; the complete record may stretch back to 2.5 million years ago.
Data from seismic and other surveys indicate that below the sediment there are about 50 to 65 m of fragmented rock deposits, and another 50 m of shocked or deformed basement rock. Sediment analysis indicate that until 18,000 years ago a lake occupied the central part of the crater, which has now become a swamp
. The crater is presently drained towards the East by the Vargem Grande creek into the adjacent Billings reservoir.
The tentative identification as an impact crater is based mainly on geomorphology
, faulting pattern, and on the exclusion of other possible formation mechanisms. In particular, there are no carbonate rock
s that could produce to karst
ic sinkhole
s. As of 2011 there were still no reports of definite evidence, such as shatter cone
s or shocked quartz
. To find such evidence one would have to drill through the sediment fill.
region of the sprawling São Paulo metropolitan area, about 35 km from the city's center. Besides the central swamp, the crater encloses remains of the native Atlantic rainforest. Starting in 1989, the northern part of the crater has been gradually occupied by irregular housing that comprise the Vargem Grande neighborhood, now home to 35,000 to 40,000 people. To prevent further degradation, the crater has been declared a protected natural landmark, registered in 1995 by the CONDEPHAAT. Its southern part was incorporated to the Capivari Monos Municipal Parkland in 1996.
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
located in the municipality of São Paulo, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. It is a round bowl-shaped depression, without any obvious central bulge, with a diameter of about 3.6 km, bounded by a circular ring of hills about 125 m high relative to the inner depression. Its approximate location is 23°52′15″ South and 46°42′30″ West, 770 m above sea level. The name comes from the town district of Colônia located just North of the feature.
Geology and ecology
Some geologists believe that the feature was created by the impact of a meteoriteMeteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
with a diameter of about 200 m. It was formed between 1 million to 20 million years ago, in crystalline basement rock
Basement Rock
Basement or Basement Rock music was a sub-genre coined in 2006 in an article by music magazine TGR. This was first in relation to the existence of underground record label Criminal Records but more for the independent bands they represent. The roots of the sub-genre are noted to be as far back as...
s 600 to 700 millions of years old. In any case, it would be one of the youngest South American impact craters known. It is partially filled by turfaceous
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
with maximum depth of 275 m, which provides a precious record of ancient environment. The upper 8 m, in particular, have provided a detailed climate
Climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
and ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
record of the last 130,000 years; the complete record may stretch back to 2.5 million years ago.
Data from seismic and other surveys indicate that below the sediment there are about 50 to 65 m of fragmented rock deposits, and another 50 m of shocked or deformed basement rock. Sediment analysis indicate that until 18,000 years ago a lake occupied the central part of the crater, which has now become a swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
. The crater is presently drained towards the East by the Vargem Grande creek into the adjacent Billings reservoir.
The tentative identification as an impact crater is based mainly on geomorphology
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
, faulting pattern, and on the exclusion of other possible formation mechanisms. In particular, there are no carbonate rock
Carbonate rock
Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite and dolostone, which is composed of the mineral dolomite .Calcite can be either dissolved by groundwater or precipitated by...
s that could produce to karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
ic sinkhole
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...
s. As of 2011 there were still no reports of definite evidence, such as shatter cone
Shatter cone
Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions...
s or shocked quartz
Shocked quartz
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure , the crystalline structure of quartz will be deformed along planes inside the crystal...
. To find such evidence one would have to drill through the sediment fill.
Urbanization and legal status
The Colônia crater is located in the suburban ParelheirosParelheiros
Parelheiros is rural district located in the extreme south of the city of São Paulo, and is also one of the districts with the largest territorial area. Very little of this area is inhabited, and is covered with reserves of the Atlantic Forest...
region of the sprawling São Paulo metropolitan area, about 35 km from the city's center. Besides the central swamp, the crater encloses remains of the native Atlantic rainforest. Starting in 1989, the northern part of the crater has been gradually occupied by irregular housing that comprise the Vargem Grande neighborhood, now home to 35,000 to 40,000 people. To prevent further degradation, the crater has been declared a protected natural landmark, registered in 1995 by the CONDEPHAAT. Its southern part was incorporated to the Capivari Monos Municipal Parkland in 1996.