– Source:Impact craters are formed when an object from space such as a meteoroid, asteroid or comet strikes the Earth at a very high velocity. This leaves an excavated circular hole on the Earth’s surface.
It is a basic geological process that has shaped the planets from their formation to today. It creates landscapes and surface materials across our solar system. The moon is covered with them, as are planets like Mercury, Mars and Venus. On Earth, impacts have influenced the evolution of life and even provided valuable mineral and energy resources. However, very few of the impact craters on Earth are visible because of various processes that obscure or erase them.
Most of the recognised impact craters on Earth are buried under sediments or have been deeply eroded. That means they no longer preserve their initial forms.
The Bosumtwi impact crater in Ghana is different, however. It is well preserved (not deeply eroded or buried under sediments). Its well-defined, near-circular basin, filled by a lake, is surrounded by a prominent crater rim that rises above the surface of the lake and an outer circular plateau. This makes it a target for several research questions.
As an Earth scientist, I joined a research team from 2019 to better understand the morphology of the crater. We carried out a morphological analysis of the crater (a study of its form, structure and geological features).
This study concluded that the activities of illegal miners are a threat to the sustainability of the crater. We also discovered that the features of the Bosumtwi impact crater can be considered as a terrestrial representation for a special type of impact crater known as rampart craters. These are common on the planets Mars and Venus and are found on icy bodies of the outer solar system (like Ganymede, Europa, Dione, Tethys and Charon).
For future studies, the Bosumtwi impact crater can be used to help understand how rampart craters form on Mars and Venus. So the Bosumtwi impact crater should be protected and preserved.
The crater
The Bosumtwi impact crater is in Ghana’s mineral-rich Ashanti gold belt. It is the location of the only natural inland lake in Ghana. As one of the world’s best-preserved young meteorite impact craters it is designated as an International Union of Geological Sciences geoheritage site.
It is one of only 190 confirmed impact crater sites worldwide, one of only 20 on the African continent. Its lake is one of six meteoritic lakes in the world, recognised for their outstanding scientific value.
At almost 1.07 million years old, the crater offers unparalleled opportunities for studying impact processes, climate history and planetary evolution. It’s an irreplaceable natural laboratory for researchers and educators.
Beyond its scientific importance, the crater holds cultural significance for the Ashanti people of Ghana. The lake at its centre serves as a sacred site and spiritual landmark. The crater’s breathtaking landscape also supports eco-tourism and local livelihoods, contributing to Ghana’s economic development while maintaining exceptional aesthetic value.
The research
As part of further research work on the 2019 study, in 2025 we have discovered through field work and satellite data analysis that illegal artisanal mining is prevalent in the area and threatening the crater. This refers to informal, labour-intensive extraction of minerals, primarily gold. It is conducted by individuals or small groups using basic tools and rudimentary machinery. The use of toxic chemicals such as mercury and cyanide, and practices such as river dredging, cause severe environmental harm.
Illegal miners are encroaching on and around the crater rim, posing severe threats to its environment and sustainability. Their activities have become more prevalent over the course of less than 10 years, indicating a growing problem. If unchecked, it could lead to irreversible damage to the crater.
These mining operations risk contaminating the lake with toxic heavy metals. The consequences of these are grave. They include destroying critical geological evidence, accelerating deforestation, and degrading the land. All this damages the crater’s scientific, cultural and economic value.
The International Union of Geological Sciences geoheritage designation of the crater underscores the urgent need for protection measures. The loss of this rare geological wonder would represent not just a national tragedy for Ghana, but a blow to global scientific heritage.
Immediate action is required. This includes enhanced satellite monitoring (tracking illegal mining, deforestation and environmental changes) using optical imagery (such as Sentinel-2, Landsat, PlanetScope). These tools can detect forest loss, identify mining pits and sediment runoff, and analyse changes over time.
Stricter enforcement of mining bans, and community engagement programmes, will help preserve the Bosumtwi impact crater’s unique attributes for future generations of scientists, students, tourists and local communities who depend on its resources.
Marian Selorm Sapah does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
By Marian Selorm Sapah, Senior lecturer, University of Ghana
