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: 200.00 km ( = 124.00 miles )
Projectile diameter: 500.00 meters ( = 1640.00 feet )
Projectile Density: 1500 kg/m3
Impact Velocity: 17.00 km per second ( = 10.60 miles per second )
Impact Angle: 45 degrees
Target Density: 1000 kg/m3
Target Type: Liquid water of depth 1000.0 meters ( = 3280.0 feet ), over crystalline rock.

Energy:

Energy before atmospheric entry: 1.42 x 1019 Joules = 3.39 x 103 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.1 x 105years

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 72500 meters = 238000 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 16.1 km/s = 10 miles/s
The impact energy is 1.28 x 1019 Joules = 3.05 x 103MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 1.36 km by 0.958 km

Crater Dimensions:

What does this mean?


The crater opened in the water has a diameter of 7.62 km ( = 4.73 miles ).

For the crater formed in the seafloor:
Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.

Transient Crater Diameter: 1.56 km ( = 0.971 miles )
Transient Crater Depth: 553 meters ( = 1810 feet )

Final Crater Diameter: 1.95 km ( = 1.21 miles )
Final Crater Depth: 416 meters ( = 1360 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 193 meters ( = 633 feet ).
The volume of the target melted or vaporized is 563000 m3 = 1.99e+07 feet3
Roughly half the melt remains in the crater

Thermal Radiation:

What does this mean?


Time for maximum radiation: 290 milliseconds after impact

Visible fireball radius: 1.54 km ( = 0.953 miles )
The fireball appears 1.74 times larger than the sun
Thermal Exposure: 3.27 x 104 Joules/m2
Duration of Irradiation: 1.01 minutes
Radiant flux (relative to the sun): 0.538


Seismic Effects:

What does this mean?


The major seismic shaking will arrive approximately 40 seconds after impact.
Richter Scale Magnitude: 5.5
Mercalli Scale Intensity at a distance of 200 km:


Ejecta:

What does this mean?


The ejecta will arrive approximately 3.43 minutes after the impact.
At your position there is a fine dusting of ejecta with occasional larger fragments
Average Ejecta Thickness: 6.67 microns ( = 0.263 thousandths of an inch )
Mean Fragment Diameter: 1.87 mm ( = 0.737 tenths of an inch )

Air Blast:

What does this mean?


The air blast will arrive approximately 10.1 minutes after impact.
Peak Overpressure: 5500 Pa = 0.055 bars = 0.781 psi
Max wind velocity: 12.7 m/s = 28.3 mph
Sound Intensity: 75 dB (Loud as heavy traffic)
Damage Description:

Tsunami Wave:

What does this mean?

The impact-generated tsunami wave arrives approximately 34.6 minutes after impact.

Tsunami wave amplitude is between: 10.2 meters ( = 33.3 feet) and 20.3 meters ( = 66.7 feet).



Tell me more...

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.






Earth Impact Effects Program Copyright 2004, Robert Marcus, H.J. Melosh, and G.S. Collins
These results come with ABSOLUTELY NO WARRANTY