A small world.
A powerful collision.

Mass = πρD³/6 and kinetic energy = ½mv² for a spherical asteroid. One megaton of TNT is 4.184 × 10¹⁵ joules. Doubling diameter multiplies mass and energy by eight; doubling speed multiplies energy by four. Angle changes the excavation estimate, not the total kinetic energy.

The transient cavity estimate uses the gravity-regime scaling in Collins, Melosh and Marcus (2005), equation 22: Dₜ = 1.161(ρᵢ/ρₜ)⅓ D⁰·⁷⁸ v⁰·⁴⁴ g⁻⁰·²² sin(θ)⅓. All inputs use SI units, target density is 2,700 kg/m³ and gravity is 9.80665 m/s². The result describes the initial excavation cavity, before crater walls collapse. It is not the final crater diameter.

Material changes bulk density. This simplified model excludes atmospheric drag, ablation, breakup, airbursts, ocean impacts, terrain strength, blast damage, tsunamis and climate effects. Small or fragile objects can break up before reaching the ground; their displayed surface-impact result is a conditional thought experiment. Small craters may be strength dominated, and very large events need detailed modeling. Shallow angles below 15° are excluded because this scaling becomes less reliable. Treat the cavity number as an approximate estimate, not a precise forecast.

Animation depicts a top-down view of the selected city, incoming direction, crater excavation, an expanding shockwave ring and debris. City streets and waterways use OpenStreetMap tiles in Web Mercator projection. The crater radius uses half the estimated transient diameter and the local metres-per-pixel scale at the impact point. The map is centered on a fixed city point; this does not model local geology, buildings or infrastructure. Building damage and debris placement are artistic, not predictions. It does not calculate an explosion radius or real event timing. Pause or scrub to explore. Reduced motion shows the result without animation.

References: Earth Impact Effects model, Collins et al. ↗ · NASA Apophis ↗ · NASA Bennu reference size and density ↗.