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: 1.61 km ( = 1.00 miles )

Projectile diameter: 100.00 meters ( = 328.00 feet )

Projectile Density: 3000 kg/m³

Impact Velocity: 17.00 km per second ( = 10.60 miles per second )

Impact Angle: 90 degrees

Target Density: 2500 kg/m³

Target Type: Sedimentary Rock

Energy:

Energy before atmospheric entry: 2.27 x 10¹⁷ Joules = 5.42 x 10¹ MegaTons TNT

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 6.0 x 10³years

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 54000 meters = 177000 ft

The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 12 km/s = 7.43 miles/s

The energy lost in the atmosphere is 1.15 x 10¹⁷ Joules = 2.74 x 10¹ MegaTons.

The impact energy is 1.12 x 10¹⁷ Joules = 2.69 x 10¹MegaTons.

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 0.411 km by 0.411 km

Crater Dimensions:

What does this mean?

Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.

Transient Crater Diameter: 1.69 km ( = 1.05 miles )

Transient Crater Depth: 597 meters ( = 1960 feet )

Final Crater Diameter: 2.11 km ( = 1.31 miles )

Final Crater Depth: 449 meters ( = 1470 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 208 meters ( = 683 feet ).

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 322 milliseconds after impact.

Richter Scale Magnitude: 5.6

Mercalli Scale Intensity at a distance of 1.61 km:

VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

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.

Ejecta:

What does this mean?


The ejecta will arrive approximately 18.1 seconds after the impact.

Your position is beneath the continuous ejecta deposit.

Average Ejecta Thickness: 17.4 meters ( = 57.1 feet )

Mean Fragment Diameter: 718 meters ( = 2360 feet )

Air Blast:

What does this mean?


The air blast will arrive approximately 4.88 seconds after impact.

Peak Overpressure: 2.85e+06 Pa = 28.5 bars = 405 psi

Max wind velocity: 1330 m/s = 2980 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.

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.