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: 100.00 km ( = 62.10 miles )

Projectile diameter: 300.00 meters ( = 984.00 feet )

Projectile Density: 3000 kg/m³

Impact Velocity: 25.00 km per second ( = 15.50 miles per second )

Impact Angle: 45 degrees

Target Density: 1000 kg/m³

Target Type: Liquid water of depth 3.0 km ( = 1.9 miles ), over crystalline rock.

Energy:

Energy before atmospheric entry: 1.33 x 10¹⁹ Joules = 3.17 x 10³ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 7.7 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 60200 meters = 198000 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 23.7 km/s = 14.7 miles/s

The energy lost in the atmosphere is 1.32 x 10¹⁸ Joules = 3.15 x 10² MegaTons.

The impact energy is 1.19 x 10¹⁹ Joules = 2.85 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 0.912 km by 0.645 km

Crater Dimensions:

What does this mean?

The crater opened in the water has a diameter of 7.64 km ( = 4.74 miles ).

For the crater formed in the seafloor:

The result of the impact is a crater field, not a single crater. The following dimensions are for the crater produced by the largest fragment.

Transient Crater Diameter: 152 meters ( = 500 feet )

Transient Crater Depth: 53.9 meters ( = 177 feet )

Final Crater Diameter: 191 meters ( = 625 feet )

Final Crater Depth: 40.6 meters ( = 133 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 18.8 meters ( = 61.7 feet ).

The volume of the target melted or vaporized is 308 m³ = 10900 feet³

Roughly half the melt remains in the crater

Thermal Radiation:

What does this mean?

Time for maximum radiation: 193 milliseconds after impact

Visible fireball radius: 3.79 km ( = 2.35 miles )

The fireball appears 8.6 times larger than the sun

Thermal Exposure: 4.46 x 10⁵ Joules/m²

Duration of Irradiation: 59.4 seconds

Radiant flux (relative to the sun): 7.51

Seismic Effects:

What does this mean?


The major seismic shaking will arrive approximately 20 seconds after impact.

Richter Scale Magnitude: 3.3

Mercalli Scale Intensity at a distance of 100 km:

Nothing would be felt. However, seismic equipment may still detect the shaking.

Ejecta:

What does this mean?

Almost no solid ejecta reaches this site.

Air Blast:

What does this mean?


The air blast will arrive approximately 5.05 minutes after impact.

Peak Overpressure: 15000 Pa = 0.15 bars = 2.13 psi

Max wind velocity: 33.3 m/s = 74.4 mph

Sound Intensity: 84 dB (Loud as heavy traffic)

Damage Description:

Glass windows will shatter.

Tsunami Wave:

What does this mean?

The impact-generated tsunami wave arrives approximately 11.8 minutes after impact.

Tsunami wave amplitude is between: 1.6 meters ( = 5.4 feet) and 40.8 meters ( = 134.0 feet).

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.