Final answer:
The cooling of lava at the beginning of Earth's history formed Earth's crust, leading to the development of the atmosphere and oceans. The study of this process falls under geology, which involves the investigation of the composition and formation of Earth's crustal layers.
Step-by-step explanation:
Near the beginning of Earth's history, when lava began to cool, it formed Earth's crust. The planet initially was molten and lacked an atmosphere and oceans. However, as it cooled, a solid crust formed. Over time, volcanoes released gases, which led to the creation of an atmosphere and, eventually, with further cooling and processes like rain, the oceans. The solid surface of the Earth, composed primarily of basaltic and granitic rocks, resulted from the cooling of volcanic lava and set the foundation for the diverse geological landscapes we find today.
The geology of our planet is fascinating, with the top layer—Earth's crust—being the most studied by geologists. Covering 55% of Earth's surface, the oceanic crust is submerged under the oceans and is about 6 kilometers thick. The continental crust, varying in thickness from 20 to 70 kilometers, and composed predominantly of granite, covers the remaining 45% of the surface. These different types of crustal rocks were formed from the cooling of volcanic lava after the molten Earth began to stabilize and cool down from its early, tumultuous beginnings.