Earth Impact Effects Program

Robert Marcus, H. Jay Melosh, and Gareth Collins

Please note: the results below are estimates based on current (limited) understanding of the impact process and come with large uncertainties; they should be used with caution, particularly in the case of peculiar input parameters. All values are given to three significant figures but this does not reflect the precision of the estimate. For more information about the uncertainty associated with our calculations and a full discussion of this program, please refer to this article

Your Inputs:

Distance from Impact: 20000.00 km ( = 12400.00 miles )
Projectile diameter: 8.05 km ( = 5.00 miles )
Projectile Density: 3000 kg/m3
Impact Velocity: 17.00 km per second ( = 10.60 miles per second )
Impact Angle: 45 degrees
Target Density: 1000 kg/m3
Target Type: Liquid water of depth 3.8 km ( = 2.4 miles ), over crystalline rock.


Energy before atmospheric entry: 1.18 x 1023 Joules = 2.83 x 107 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 6.0 x 107years

Major Global Changes:

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundreths of a degree).
The impact does not shift the Earth's orbit noticeably.

Crater Dimensions:

What does this mean?

The crater opened in the water has a diameter of 85.8 km ( = 53.3 miles ).

For the crater formed in the seafloor:
Transient Crater Diameter: 46.1 km ( = 28.6 miles )
Transient Crater Depth: 16.3 km ( = 10.1 miles )

Final Crater Diameter: 76.3 km ( = 47.4 miles )
Final Crater Depth: 1.09 km ( = 0.677 miles )
The crater formed is a complex crater.
The volume of the target melted or vaporized is 414 km3 = 99.3 miles3
Roughly half the melt remains in the crater, where its average thickness is 248 meters ( = 813 feet ).

Thermal Radiation:

What does this mean?

The fireball is below the horizon. There is no direct thermal radiation.

Seismic Effects:

What does this mean?

The major seismic shaking will arrive approximately 1.11 hours after impact.
Richter Scale Magnitude: 9.4
Mercalli Scale Intensity at a distance of 20000 km:


What does this mean?

Little rocky ejecta reaches this site; fallout is dominated by condensed vapor from the projectile.

Air Blast:

What does this mean?

The air blast will arrive approximately 16.8 hours after impact.
Peak Overpressure: 871 Pa = 0.00871 bars = 0.124 psi
Max wind velocity: 2.04 m/s = 4.57 mph
Sound Intensity: 59 dB (Loud as heavy traffic)
Damage Description:

Tsunami Wave:

What does this mean?

The impact-generated tsunami wave arrives approximately 28.9 hours after impact.

Tsunami wave amplitude is between: 8.2 meters ( = 26.7 feet) and 16.3 meters ( = 53.5 feet).

Tell me more...

Click here for a pdf document that details the observations, assumptions, and equations upon which this program is based. It describes our approach to quantifying the important impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions. The processes included are: atmospheric entry, impact crater formation, fireball expansion and thermal radiation, ejecta deposition, seismic shaking, and the propagation of the atmospheric blast wave.

Earth Impact Effects Program Copyright 2004, Robert Marcus, H.J. Melosh, and G.S. Collins
These results come with ABSOLUTELY NO WARRANTY