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: 1000.00 km ( = 621.00 miles )

Projectile diameter: 2.70 km ( = 1.68 miles )

Projectile Density: 3000 kg/m³

Impact Velocity: 31.00 km per second ( = 19.30 miles per second )

Impact Angle: 30 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 1.49 x 10²² Joules = 3.55 x 10⁶ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.2 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?

Transient Crater Diameter: 26.6 km ( = 16.5 miles )

Transient Crater Depth: 9.41 km ( = 5.84 miles )

Final Crater Diameter: 41 km ( = 25.5 miles )

Final Crater Depth: 905 meters ( = 2970 feet )

The crater formed is a complex crater.

The volume of the target melted or vaporized is 65.7 km³ = 15.8 miles³

Roughly half the melt remains in the crater, where its average thickness is 118 meters ( = 388 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 3.33 minutes after impact.

Richter Scale Magnitude: 9.0

Mercalli Scale Intensity at a distance of 1000 km:

III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck.

IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

Ejecta:

What does this mean?


The ejecta will arrive approximately 8.24 minutes after the impact.

At your position there is a fine dusting of ejecta with occasional larger fragments

Average Ejecta Thickness: 4.48 mm ( = 1.76 tenths of an inch )

Mean Fragment Diameter: 604 microns ( = 23.8 thousandths of an inch )

Air Blast:

What does this mean?


The air blast will arrive approximately 50.5 minutes after impact.

Peak Overpressure: 16900 Pa = 0.169 bars = 2.39 psi

Max wind velocity: 37.1 m/s = 83.1 mph

Sound Intensity: 85 dB (Loud as heavy traffic)

Damage Description:

Glass windows will shatter.

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.