Colônia
Key facts
- Country
- Brazil
- Diameter
- 3.6 km
- Age
- between about 5 and 36 million years
- Location
- 23.87° S, 46.70° W
A round basin about 3.6 km across on the southern edge of the city of São Paulo, ringed by a low wooded rim. Its floor is a peat bog, and houses are spreading over the rim.
Colônia is an impact crater about 3.6 km across on the southern outskirts of São Paulo, Brazil, one of the largest cities in the world. It is one of very few impact craters inside a major city.
What can be seen. The crater is a round basin ringed by hills about 125 m higher than its floor. The floor holds a thick layer of sediment and peat, a bog formed from plant remains that have accumulated over millions of years. A river has cut through the rim on one side. Parts of the basin are protected, but housing is spreading over the rim.
What it hit. The impactor struck crystalline basement rocks, about 600 to 700 million years old. The crater bowl then filled slowly with sediment and peat, which today is up to about 275 m thick.
Proof of impact. The round shape was noticed on aerial photographs in the 1960s. The area has no limestone, so it cannot be a sinkhole, and the pattern of faults and the shape of the basin fit an impact. Gravity and seismic surveys show a deep bowl with broken and deformed basement rock beneath the fill. Drilling through the sediment to sample shocked rock directly is still hoped for.
Age. The age is poorly known. The thickness of the sediment fill and the history of the region's rivers suggest it formed between about 5 and 36 million years ago.
Why it matters. The sediments filling Colônia hold a long record of past climate and vegetation in South America, valuable to scientists studying how the climate has changed. The impactor is unknown.
Did you know?
Colônia lies within the city of São Paulo, one of the largest cities in the world.
Its floor holds a thick bog of peat and sediment.
The crater was noticed on aerial photographs in the 1960s.