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: 1000.00 meters ( = 3280.00 feet )

Projectile Density: 3000 kg/m³

Impact Velocity: 51.00 km per second ( = 31.70 miles per second )

Impact Angle: 45 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: 2.04 x 10²¹ Joules = 4.88 x 10⁵ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.6 x 10⁶years

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 71600 meters = 235000 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 50.7 km/s = 31.5 miles/s

The energy lost in the atmosphere is 2.68 x 10¹⁹ Joules = 6.39 x 10³ MegaTons.

The impact energy is 2.02 x 10²¹ Joules = 4.82 x 10⁵MegaTons.

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 1.63 km by 1.15 km

Crater Dimensions:

What does this mean?

The crater opened in the water has a diameter of 27.3 km ( = 16.9 miles ).

For the crater formed in the seafloor:

Transient Crater Diameter: 4.26 km ( = 2.65 miles )

Transient Crater Depth: 1.51 km ( = 0.936 miles )

Final Crater Diameter: 5.17 km ( = 3.21 miles )

Final Crater Depth: 485 meters ( = 1590 feet )

The crater formed is a complex crater.

The volume of the target melted or vaporized is 0.0257 km³ = 0.00617 miles³

Roughly half the melt remains in the crater, where its average thickness is 1.8 meters ( = 5.91 feet ).

Thermal Radiation:

What does this mean?

Time for maximum radiation: 499 milliseconds after impact

Visible fireball radius: 24.5 km ( = 15.2 miles )

The fireball appears 55.6 times larger than the sun

Thermal Exposure: 9.25 x 10⁷ Joules/m²

Duration of Irradiation: 5.47 minutes

Radiant flux (relative to the sun): 282

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 20 seconds after impact.

Richter Scale Magnitude: 6.6

Mercalli Scale Intensity at a distance of 100 km:

IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.

Ejecta:

What does this mean?


The ejecta will arrive approximately 2.4 minutes after the impact.

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

Average Ejecta Thickness: 2.94 mm ( = 1.16 tenths of an inch )

Mean Fragment Diameter: 3.2 cm ( = 1.26 inches )

Air Blast:

What does this mean?


The air blast will arrive approximately 5.05 minutes after impact.

Peak Overpressure: 414000 Pa = 4.14 bars = 58.9 psi

Max wind velocity: 458 m/s = 1020 mph

Sound Intensity: 112 dB (May cause ear pain)

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 overturned and displaced, requiring major repairs.

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 7.9 minutes after impact.

Tsunami wave amplitude is between: 113.0 meters ( = 370.0 feet) and 521.0 meters ( = 1710.0 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.