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: 1.00 meters ( = 3.28 feet )

Projectile diameter: 6.20 cm ( = 2.44 inches )

Projectile Density: 8000 kg/m³

Impact Velocity: 11.00 km per second ( = 6.83 miles per second )

Impact Angle: 72 degrees

Target Density: 1000 kg/m³

Target Type: Liquid water of depth 61.0 cm ( = 24.0 inches ), over crystalline rock.

Energy:

Energy before atmospheric entry: 6.05 x 10⁷ Joules = 0.14 x 10^-7 MegaTons TNT

The average interval between impacts of this size somewhere on Earth is less than 1 month.

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 lands intact, with a velocity 0.011 km/s = 0.00683 miles/s.

The energy lost in the atmosphere is 6.05 x 10⁷ Joules = 0.14 x 10^-7 MegaTons.

Crater Dimensions:

What does this mean?

The crater opened in the water has a diameter of 53.4 cm ( = 21 inches ).

For the crater formed in the seafloor:

Transient Crater Diameter: 15.4 cm ( = 6.08 inches )

Transient Crater Depth: 5.46 cm ( = 2.15 inches )

Final Crater Diameter: 19.3 cm ( = 7.6 inches )

Final Crater Depth: 4.11 cm ( = 1.62 inches )

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 1.9 cm ( = 0.75 inches ).

At this impact velocity ( < 12 km/s), little shock melting of the target occurs.

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 Richter Scale Magnitude for this impact is less than zero; no seismic shaking will be felt.

Ejecta:

What does this mean?

Most ejecta is blocked by Earth's atmosphere

Air Blast:

What does this mean?


The air blast will arrive approximately 3.03 milliseconds after impact.

Peak Overpressure: 5.18e+06 Pa = 51.8 bars = 735 psi

Max wind velocity: 1810 m/s = 4050 mph

Sound Intensity: 134 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?

The impact-generated tsunami wave arrives approximately 776.0 milliseconds after impact.

Tsunami wave amplitude is less than 10 cm at your location.

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.