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: 10.00 cm ( = 3.94 inches )

Projectile diameter: 100.00 meters ( = 328.00 feet )

Projectile Density: 8000 kg/m³

Impact Velocity: 60.00 km per second ( = 37.30 miles per second )

Impact Angle: 10 degrees

Target Density: 1000 kg/m³

Target Type: Liquid water of depth 4.0 km ( = 2.5 miles ), over crystalline rock.

Energy:

Energy before atmospheric entry: 7.54 x 10¹⁸ Joules = 1.80 x 10³ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 3.5 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 34400 meters = 113000 ft

The projectile bursts into a cloud of fragments at an altitude of 8380 meters = 27500 ft

The residual velocity of the projectile fragments after the burst is 31.2 km/s = 19.4 miles/s

The energy of the airburst is 5.50 x 10¹⁸ Joules = 1.31 x 10³ MegaTons.

Large fragments strike the surface and may create a crater strewn field. A more careful treatment of atmospheric entry is required to accurately estimate the size-frequency distribution of meteoroid fragments and predict the number and size of craters formed.

Air Blast:

What does this mean?


The air blast will arrive approximately 25.4 seconds after impact.

Peak Overpressure: 4.11e+06 - 8.21e+06 Pa = 41.1 - 82.1 bars = 583 - 1170 psi

Max wind velocity: 1610 m/s = 3600 mph

Sound Intensity: 132 dB (Dangerously Loud)

Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.

Highway truss bridges will collapse.

Highway girder bridges will collapse.

Glass windows will shatter.

Cars and trucks will be largely displaced and grossly distorted and will require rebuilding before use.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

Tsunami Wave:

What does this mean?

Your location is within the crater formed in the water layer. This is where the impact tsunami wave is generated.

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.