Crater is circular and the debris that is kicked up during impact will cover a greater area than the hole itself. More small craters than large ones because more small meteors than large ones. Largest meteor craters are called impact basins . Small ones burn up in atmospheres of Venus, Earth and Mars, but survive to crash on surfaces of Mercury and the Moon. This allows us to roughly date the surface of the planet.
More craters means oldest, few craters means geologically younger.
Used to date rivers on Mars, for example. Consistency of lava determines what it looks like on the surface. Least runny makes steep-sided volcanoes like Mt. St. Helens. Lava moves slowly and solidifies before traveling far. Need high internal temperature and thin lithosphere to get volcanoes .