Asteroid Impact effects calculator....

[Hammyton]

Here

At a distance of 600km from a 30km diameter asteroid going 80km/s....

The average interval between impacts of this size somewhere on Earth is 2.9 x 1010years

Final Crater Diameter: 1457.50 km = 905.10 miles

Visible fireball radius: 1397.0 km = 867.6 miles
The fireball appears 529.2 times larger than the sun

The ejecta will arrive approximately 369.5 seconds after the impact.

Average Ejecta Thickness: 7464.1 m = 24488.44 ft

Max wind velocity: 298.1 m/s = 666.9 mph

 

[FoBoT]

that large of a hit would be quite bad

 

[DrPizza]

I find this to be scarier... check out the average interval between impact of this size
(btw, your one per 2.9*10^10 years means the earth gets hit by one of that size every 29,000,000,000 years. That's longer than the earth has been around... doesn't sound quite right. )


Your Inputs:
Distance from Impact: 1000.00 km = 621.00 miles
Projectile Diameter: 15.00 m = 49.20 ft = 0.01 miles
Projectile Density: 8000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 45 degrees
Target Density: 1500 kg/m3
Target Type: Competent Rock or saturated soil
Energy:
2.04 x 1015 Joules = 488.01 KiloTons TNT
The average interval between impacts of this size somewhere on Earth is 63.3 years
Crater Size:
What does this mean?



Transient Crater Diameter: 657 m = 2156 ft
Final Crater Diameter: 1025 m = 3363 ft

wouldn't it be kinda cool to see a video of one that size hitting a city? (of course, with plenty of warning to evacuate the city and set up the cameras)