Final answer:
The era of planet formation ended due to the dissipation of the dust disk and the era of giant impacts.
Step-by-step explanation:
The era of planet formation ended as a result of two major events: the dissipation of the dust disk and the era of giant impacts.
After the dust disk dissipated, the planets in our solar system started to cool and assume their present aspects. This marked the end of the era of giant impacts, which lasted for about 100 million years. During this era, planetesimals crashed into each other and disrupted the growing planets, causing all the planets to become heated and differentiated.