Final answer:
The dark rock seen in the formation is a xenolith, which is a fragment of rock encompassed by an igneous body that did not ascend from the initial magma.
Step-by-step explanation:
The dark rock in the photograph that was incorporated into magma and subsequently solidified within the lighter colored igneous rock is identified as a xenolith. Covered in igneous rock terminology, this concept is readily understood when considering the origins of intrusive and extrusive igneous rocks. Intrusive rocks, like granite, are formed from magma that cools slowly inside the Earth, allowing the formation of large, coarse-grained crystals. In contrast, extrusive rocks like basalt and rhyolite, solidify more quickly on the Earth's surface from lava, resulting in a fine-grained texture. A xenolith, meaning 'foreign rock', is a piece of rock within an igneous body that was not derived from the original magma but rather was incorporated from a surrounding rock formation.
The dark rock in the photograph is an example of a xenolith. Xenoliths are fragments of rock that are different from the surrounding igneous rock and are incorporated into the magma during the solidification process. In this case, the dark rock was broken off from a magma conduit wall and then surrounded by lighter-colored igneous rock that solidified.