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The core is Earth's deepest layer. It is a ball of solid iron just larger than Pluto which is surrounded by a liquid outer core.
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During this interval, a disproportionately large number of asteroids are theorized to have collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars.
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The earth grew from the accumulation of planetismals (meteorites and asteroids) over a period of 1-200 million years
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By 4 billion years ago the earth had cooled enough for the outer layers to have solidified and for oceans to form.
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Perhaps Earth's gravity snagged a passing body.