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: 2040.00 km ( = 1270.00 miles )

Projectile diameter: 150.00 km ( = 93.20 miles )

Projectile Density: 1000 kg/m³

Impact Velocity: 1340.00 km per second ( = 830.00 miles per second ) (Your chosen velocity is higher than the maximum for an object orbiting the sun)

Impact Angle: 90 degrees

Target Density: 1000 kg/m³

Target Type: Liquid water of depth 2040.0 km ( = 1270.0 miles ), over crystalline rock.

Energy:

Energy before atmospheric entry: 1.58 x 10³⁰ Joules = 3.77 x 10¹⁴ MegaTons TNT

The average interval between impacts of this size is longer than the Earth's age.

Such impacts could only occur during the accumulation of the Earth, between 4.5 and 4 billion years ago.

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?

The crater opened in the water has a diameter of 4460 km ( = 2770 miles ).

For the crater formed in the seafloor:

Transient Crater Diameter: 520 meters ( = 1700 feet )

Transient Crater Depth: 184 meters ( = 603 feet )

Final Crater Diameter: 650 meters ( = 2130 feet )

Final Crater Depth: 138 meters ( = 454 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 64.1 meters ( = 210 feet ).

The volume of the target melted or vaporized is 4040 m³ = 143000 feet³

Roughly half the melt remains in the crater

Thermal Radiation:

What does this mean?

Time for maximum radiation: 17.4 seconds after impact

Your position is inside the fireball.

The fireball appears 2560 times larger than the sun

Thermal Exposure: 1.78 x 10¹⁴ Joules/m²

Duration of Irradiation: 84 hours

Radiant flux (relative to the sun): 587000

Effects of Thermal Radiation:

Clothing ignites

Much of the body suffers third degree burns

Newspaper ignites

Plywood flames

Deciduous trees ignite

Grass ignites

Seismic Effects:

What does this mean?


The major seismic shaking will arrive approximately 6.8 minutes after impact.

Richter Scale Magnitude: 4.0

Mercalli Scale Intensity at a distance of 2040.100 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 1.72 hours after impact.

Peak Overpressure: 2.38e+09 Pa = 23800 bars = 338000 psi

Max wind velocity: 39300 m/s = 87900 mph

Sound Intensity: 188 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.