Lunar 100 – Object 49
Gruithuisen Delta and Gamma are two prominent volcanic domes located on the northern edge of Oceanus Procellarum, formed by unusually viscous lavas unlike the fluid basalts that dominate most lunar volcanism. Their steep slopes, rounded summits, and elevated profiles indicate slow, silica‑rich eruptions that built thick, dome‑shaped structures rather than broad, shallow shields. These domes are included in the Lunar 100 because they represent rare examples of viscous lunar volcanism, offering insight into diverse magmatic processes that operated on the Moon.