Evidence indicates that the impact
angle was about 30 degrees above the horizon,
1. Artemieva, N. 2008. Tektites: Model Versus Reality.
39th Lunar and Planetary Science Conference, p. 1651.
The giant meteorite had penetrated completely through the continental crust when it exploded, transferring its energy directly to the surrounding crust. Some debris went straight up, unlike an aboveground explosion which spreads devastation across a wide surface area.
Putting the scattered pieces of Earth's crust back together reveals the hole where the giant meteorite vaporized and excavated the continental crust, including the side blowouts. Based on the distance from the center to the Comoros and Amirante Trench, the crater was over 500 miles in diameter. By comparison, Chicxulub crater is 112 miles in diameter.
The remnants of the crater walls can still be seen as rounded cuts on the coasts of East Africa, northern Madagascar, and southern Australia
impact was onto continental crust. But as the land separated,
the ocean rushed in and obliterated the crater rim. This is
typical for craters in the ocean.
Yet some effects are evident on the west side. The coasts of Kenya and Tanzania show severe faulting and diapirism (cracks into which magma seeped). The continental shelf is quite narrow (25 to 50 km), with a steep continental slope. Numerous normal (pull-apart) faults are downthrown to the east. There is a major sediment slide 8 kilometers thick.1 Such partial collapse is typical of impacts on the continental margin.2
1. Coffin, M.F., P.D. Rabinowitz. 1988. Evolution of the conjugate East-African-Madagascan margins and the Western Somali Basin. Geological Society of America Special Paper 226.
2. Dypvik, Henning, Lubomir F. Jansa. 2003. Sedimentary signatures and processes during marine bolide impacts: a review. Sedimentary Geology, Vol. 161, pp. 309-337.
Global seismic tomography shows the depth and extent of the damage of the impact. The cross-section C to C' (below) passes through East Africa. C' is the part of Africa nearest the impact site.
Here is what the tomographic cross-section reveals:
is right where we expect it - at the point of maximum damage.
We would expect that the shock wave would produce high-pressure metamorphism in the rocks of east Tanzania, and that is what we find: "Peak metamorphic conditions are surprisingly similar over a very large area", about 140,000 square kilometers! High-pressure granulite facies metamorphism is evident throughout the Pan-African mobile belt of East Africa. Note that Plate Tectonics theory sees this as an area where crust separated rather than being crushed together before splitting.
Appel, P., A. Moeller, V. Schenk. 1998. High-pressure granulite facies metamorphism in the Pan-African belt of eastern Tanzania: P-T-t evidence against granulite formation by continent collision. Journal of Metamorphic Geology, Vol. 16, No. 4, 491-510.
Regrettably, the West Somali Basin basalt floor has scarcely been sampled. Drilling was attempted at two sites (240 and 241) in 1972 as part of the Deep Sea Drilling Project. The drill bit broke after penetrating just 1.2 meters into basalt at site 240, and never reached basalt at site 241. No one ever tried again.