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: 26.00 km ( = 16.10 miles )
Projectile diameter: 140.00 meters ( = 459.00 feet )
Projectile Density: 3000 kg/m3
Impact Velocity: 17.00 km per second ( = 10.60 miles per second )
Impact Angle: 90 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 6.23 x 1017 Joules = 1.49 x 102 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.5 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 54000 meters = 177000 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 14.8 km/s = 9.16 miles/s
The impact energy is 4.69 x 1017 Joules = 1.12 x 102MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 0.423 km by 0.423 km

Crater Dimensions:

What does this mean?


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

Transient Crater Diameter: 2.41 km ( = 1.49 miles )
Transient Crater Depth: 851 meters ( = 2790 feet )

Final Crater Diameter: 3.01 km ( = 1.87 miles )
Final Crater Depth: 641 meters ( = 2100 feet )
The crater formed is a simple crater

The floor of the crater is underlain by a lens of broken rock debris (breccia) with a maximum thickness of 297 meters ( = 974 feet ).
The volume of the target melted or vaporized is 0.00417 km3 = 0.001 miles3
Roughly half the melt remains in the crater

Thermal Radiation:

What does this mean?


At this impact velocity ( < 15 km/s), little vaporization occurs; no fireball is created, therefore, there is no thermal radiation damage.

Seismic Effects:

What does this mean?


The major seismic shaking will arrive approximately 5.2 seconds after impact.
Richter Scale Magnitude: 6.0
Mercalli Scale Intensity at a distance of 26 km:


Ejecta:

What does this mean?


The ejecta will arrive approximately 1.22 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments
Average Ejecta Thickness: 1.71 cm ( = 0.672 inches )
Mean Fragment Diameter: 65.1 cm ( = 25.6 inches )

Air Blast:

What does this mean?


The air blast will arrive approximately 1.31 minutes after impact.
Peak Overpressure: 23600 Pa = 0.236 bars = 3.35 psi
Max wind velocity: 50.7 m/s = 113 mph
Sound Intensity: 87 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.






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