There are many types of rocks on Earth, but they can generally be classified into three major categories: igneous rocks, metamorphic rocks, and sedimentary rocks.

Let's discuss the origins of some common rocks within each category.

First, it's important to clarify a few concepts. The lithosphere and the crust are not the same. The lithosphere includes the uppermost mantle in addition to the crust, while the crust is further divided into oceanic crust and continental crust.

When we talk about "plates," we're referring to the lithosphere. If a plate consists mostly of oceanic crust, it's an oceanic plate; if it has a significant continental crust above it, it's a continental plate. Second, rocks and minerals are different. Rocks are mixtures of one or more minerals, while minerals are naturally occurring pure substances. Third, the mantle is not liquid but undergoes slow convection.

Now, let's discuss the formation of rocks.

Initially, Earth and the other planets in the solar system formed simultaneously. Earth started as a chaotic entity similar in structure to chondrites and lacked the layering of the core, mantle, and crust.

About 50 million years after Earth formed, a Mars-sized planet called Theia collided with Earth, generating immense energy that nearly melted the planet (some material was ejected to form the moon). During this process, Earth began to differentiate. Heavier materials like iron and nickel sank towards the center, forming the iron-rich core.

Lighter elements such as magnesium, aluminum, silicon, carbon, oxygen, calcium, and sodium remained outside the core, forming the primitive mantle. As heavier materials sank, gravitational potential energy was released, allowing the mantle to absorb energy, maintain temperature, and undergo convection, which contributed to the formation of the geomagnetic field.

Subsequently, Earth entered a cooling phase, and heat was radiated into space. The outer layers cooled more quickly, causing some minerals to solidify (e.g., garnet, spinel, olivine, pyroxene) below their melting points.

These minerals formed solid crystals in the upper mantle, creating rocks like lherzolite, peridotite, dunite, pyroxenite, harzburgite, and websterite, constituting the early lithosphere. These rocks varied in thickness, with weaker areas becoming plate boundaries. During this time, comets brought water to Earth, leading to the formation of oceans above the rocks.

From these initial rocks, various types of rocks formed later. Volcanic activity created various igneous rocks (including the aforementioned ultramafic rocks).

Metamorphic rocks typically form under high temperature and pressure conditions. Besides subduction zones, another environment for metamorphic rock formation is in mountainous regions, especially where two continental plates collide, such as the Himalayas and the Alps.

Metamorphic rocks formed on a large scale in these regions are called regional metamorphic rocks and are further classified into various facies based on the temperature and pressure conditions during formation.

Another major category of rocks is sedimentary rocks. Unlike metamorphic rocks, which often form in tectonically active subduction zones, sedimentary rocks generally form in less active continental shelf shallow seas and seabeds, as well as extensively on the Earth's surface. Igneous and metamorphic rocks are eroded physically or chemically (by water, glaciers, plants, wind, tides, etc.) and transported elsewhere by water or air.

In low-energy environments (plains, lakes, beaches, shallow seas, alluvial fans, deltas, etc.), these fragments settle. Larger particles settle first, usually at the bottom of the sediment layer or closer to their source. Smaller particles can be carried farther away, such as into the deep sea.

The three major types of rocks can undergo mutual transformation or self-transformation. For example, metamorphic and sedimentary rocks may be subducted into the mantle and melted, and when they are erupted back to the surface, they become igneous rocks.

Igneous and metamorphic rocks, through erosion, sedimentation, etc., can form sedimentary rocks. Under high temperature and pressure conditions, igneous and sedimentary rocks can also form metamorphic rocks.