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: 5000.00 km ( = 3110.00 miles )

Projectile diameter: 1200.00 km ( = 745.00 miles )

Projectile Density: 1500 kg/m³

Impact Velocity: 2.30 km per second ( = 1.43 miles per second )

Impact Angle: 30 degrees

Target Density: 1000 kg/m³

Target Type: Liquid water of depth 5.0 km ( = 3.1 miles ), over crystalline rock.

Energy:

Energy before atmospheric entry: 3.59 x 10²⁷ Joules = 8.58 x 10¹¹ 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).

Depending on the direction and location of impact, the collision may cause a change in the length of the day of up to 3.52 minutes.

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 1250 km ( = 775 miles ).

For the crater formed in the seafloor:

Transient Crater Diameter: 380 km ( = 236 miles )

Transient Crater Depth: 134 km ( = 83.5 miles )

Final Crater Diameter: 828 km ( = 514 miles )

Final Crater Depth: 2.24 km ( = 1.39 miles )

The crater formed is a complex crater.

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 major seismic shaking will arrive approximately 16.7 minutes after impact.

Richter Scale Magnitude: 12.6 (This is greater than any earthquake in recorded history)

Mercalli Scale Intensity at a distance of 5000 km:

VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.

Ejecta:

What does this mean?


The ejecta will arrive approximately 26.2 minutes after the impact.

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

Average Ejecta Thickness: 1.49 meters ( = 4.89 feet )

Mean Fragment Diameter: 188 microns ( = 7.39 thousandths of an inch )

Air Blast:

What does this mean?


The air blast will arrive approximately 4.21 hours after impact.

Peak Overpressure: 2.95e+06 Pa = 29.5 bars = 419 psi

Max wind velocity: 1360 m/s = 3040 mph

Sound Intensity: 129 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 6.3 hours after impact.

Tsunami wave amplitude is between: 624.0 meters ( = 2050.0 feet) and 1.2 km ( = 0.8 miles).

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.