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: 70.00 km ( = 43.50 miles )
Projectile diameter: 400.00 meters ( = 1310.00 feet )
Projectile Density: 2500 kg/m3
Impact Velocity: 17.00 km per second ( = 10.60 miles per second )
Impact Angle: 45 degrees
Target Density: 2750 kg/m3
Target Type: Crystalline Rock


Energy before atmospheric entry: 1.21 x 1019 Joules = 2.89 x 103 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 9.9 x 104years

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.

Atmospheric Entry:

The projectile begins to breakup at an altitude of 59500 meters = 195000 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 16.4 km/s = 10.2 miles/s
The energy lost in the atmosphere is 8.71 x 1017 Joules = 2.08 x 102 MegaTons.
The impact energy is 1.12 x 1019 Joules = 2.68 x 103MegaTons.
The larger of these two energies is used to estimate the airblast damage.
The broken projectile fragments strike the ground in an ellipse of dimension 1.05 km by 0.742 km

Crater Dimensions:

What does this mean?

Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.

Transient Crater Diameter: 4.64 km ( = 2.88 miles )
Transient Crater Depth: 1.64 km ( = 1.02 miles )

Final Crater Diameter: 5.7 km ( = 3.54 miles )
Final Crater Depth: 500 meters ( = 1640 feet )
The crater formed is a complex crater.
The volume of the target melted or vaporized is 0.0707 km3 = 0.017 miles3
Roughly half the melt remains in the crater, where its average thickness is 4.18 meters ( = 13.7 feet ).

Thermal Radiation:

What does this mean?

Time for maximum radiation: 274 milliseconds after impact

Visible fireball radius: 4.09 km ( = 2.54 miles )
The fireball appears 13.3 times larger than the sun
Thermal Exposure: 9.75 x 105 Joules/m2
Duration of Irradiation: 58.2 seconds
Radiant flux (relative to the sun): 16.8 (Flux from a burner on full at a distance of 10 cm)

Effects of Thermal Radiation:

Seismic Effects:

What does this mean?

The major seismic shaking will arrive approximately 14 seconds after impact.
Richter Scale Magnitude: 6.9
Mercalli Scale Intensity at a distance of 70 km:


What does this mean?

The ejecta will arrive approximately 2 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments
Average Ejecta Thickness: 1.21 cm ( = 0.476 inches )
Mean Fragment Diameter: 9.11 cm ( = 3.58 inches )

Air Blast:

What does this mean?

The air blast will arrive approximately 3.54 minutes after impact.
Peak Overpressure: 26600 Pa = 0.266 bars = 3.78 psi
Max wind velocity: 56.6 m/s = 127 mph
Sound Intensity: 88 dB (Loud as heavy traffic)
Damage Description:

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.

Recent improvements in the airblast calculation are described here.

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