expanse
n.a wide, open area of land, water, or sky. It describes a space that feels very large and goes on for a long distance.
n.a wide, continuous area or stretch of something, typically land or sea. Often used to emphasize the vastness or uninterrupted nature of a physical space.
“The blue expanse of the ocean stretched out before us.”
“From the top of the hill, we could see the vast expanse of the valley below us.”
“The hikers were struck by the silent expanse of the desert, where the horizon seemed to recede further with every step they took toward the distant mountains.”
Often paired with the preposition 'of' to describe the material or element filling the space.
“For the study, the researchers looked at the vast expanse of volcanic rock that erupted from the Lauca Caldera in northern Chile 21.9 million years ago.”
From Latin expansum, from expandō.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.