Well, according to the calculator, nothing major happens on a global scale. The collision would be survivable by many in a city.
This is accounting for a 1,000 ft IRON meteor coming in at 50 degrees (most likely is 45) hitting ANY area.
Why are we worried now?
using
http://www.lpl.arizona.edu/impacteffects/
Your Inputs:
Distance from Impact: 100.00 km = 62.10 miles
Projectile Diameter: 1000.00 m = 3280.00 ft = 0.62 miles
Projectile Density: 8000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 30 degrees
Target Density: 2750 kg/m3
Target Type: Crystalline Rock
Energy:
Energy before atmospheric entry: 6.05 x 1020 Joules = 1.45 x 105 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 1.0 x 106years
Atmospheric Entry:
The projectile begins to breakup at an altitude of 14200 meters = 46500 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 16.9 km/s = 10.5 miles/s
The impact energy is 6.02 x 1020 Joules = 1.44 x 105MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 2.09 km by 1.04 km
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 Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
Crater Dimensions:
What does this mean?
Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.
Transient Crater Diameter: 12.6 km = 7.85 miles
Transient Crater Depth: 4.47 km = 2.78 miles
Final Crater Diameter: 17.7 km = 11 miles
Final Crater Depth: 0.703 km = 0.436 miles
The crater formed is a complex crater.
The vol of the target melted/vaporized is 2.68 km3=0.642 mi3
Roughly half the melt remains in the crater , where its average thickness is 21.3 meters = 69.9 feet
Thermal Radiation:
Time for maximum radiation: 0.996 seconds after impact
Visible fireball radius: 16.1 km = 10 miles
The fireball appears 36.6 times larger than the sun
Thermal Exposure: 2.70 x 107 Joules/m2
Duration of Irradiation: 219 seconds
Radiant flux (relative to the sun): 123
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:
The major seismic shaking will arrive at approx 20 seconds.
Richter Scale Magnitude: 8.1
Mercalli Scale Intensity at a distance of 100 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:
The ejecta will arrive approx 144 seconds after the impact.
Average Ejecta Thickness: 22.8 cm = 8.99 inches
Mean Fragment Diameter: 11.4 cm = 4.47 inches
Air Blast:
The air blast will arrive at approximately 303 seconds.
Peak Overpressure: 176000 Pa = 1.76 bars = 24.9 psi
Max wind velocity: 262 m/s = 585 mph
Sound Intensity: 105 dB (May cause ear pain)
Damage Description:
Multistory wall-bearing buildings will collapse.
Wood frame buildings will almost completely collapse.
Highway truss bridges will collapse.
Glass windows will shatter.
Up to 90 percent of trees blown down; remainder stripped of branches and leaves.