#volcanic

• Crowded — As an adjective, crowded, packed with people or objects, or formed from closely joined elements. As a neuter noun, in geology, it represents a sedimentary or volcanic rock formed through the natural cementing of large angular fragments, while in technology, a product obtained by compacting and binding powdery or fibrous materials.
• Agung — An active stratovolcano located on the island of Bali, Indonesia, representing the highest geographical point of the island, with an elevation exceeding three thousand meters. In local Indonesian culture and Balinese Hinduism, this mountain is considered deeply sacred, viewed as the central axis of the universe and the dwelling place of the gods, hosting the famous Pura Besakih temple complex on its slopes.
• Ahaggar — A mountainous massif of volcanic origin located in the center of the Sahara Desert, in southern Algeria, characterized by dramatic landscapes made of steep peaks, high plateaus, and spectacular basalt formations. Also known as the Hoggar Mountains, this geographical hub is historically inhabited by Tuareg populations and contains priceless prehistoric archaeological remains, including famous rock paintings.
• Allophane — An amorphous or poorly crystalline hydrated aluminum silicate mineral, often associated with the weathering of volcanic rocks and ash deposits in humid environments. This structural compound exhibits a variable chemical composition and a gelatinous or vitreous texture, holding significant importance in soil science due to its high cation exchange capacity and phosphate-fixing ability in andosols.
• Allophane — Minerals from the hydrated aluminum silicate class, amorphous or poorly crystalline, which form structurally through the weathering of volcanic rocks (ash and basalt) under the action of meteoric waters; they are characterized by high porosity and a large ion-exchange capacity, being specific to andosol-type soils.
• Alunitization — A geological process of acid hydrothermal alteration of volcanic or magmatic rocks rich in feldspars, under the action of ascending solutions charged with sulfuric acid; the act of transforming into alunite. This structural phenomenon leads to the replacement of primary minerals with alunite, quartz, and kaolinite, constituting a valuable indicator in geological prospecting for metalliferous deposits.
• Andesite — An effusive (volcanic) igneous rock with a microlitic or porphyritic texture, gray, brown, or greenish in color, mainly composed of plagioclase feldspar (such as andesine) and ferromagnesian minerals (amphiboles, pyroxenes, or biotite). It has a wide distribution in eruption areas and is intensely used in construction as dimension stone, paving, gravel, or structural aggregate due to its hardness.
• Andesite — An obsolete linguistic variant or synonymous regional form of the standard term 'andezit', historically used in some mining treatises or technical translations to describe the effusive volcanic rock with a microlitic texture. It represents a feminine morphological adaptation of the international petrographic name, abandoned in modern geological standards in favor of the neuter form.
• Andesitic — Belonging to andesite, relating to andesite, or having the composition, structure, and characteristics specific to this effusive igneous rock. In petrography, it describes magmas, lavas, tuffs, or volcanic flows with an intermediate silica content, characteristic of tectonic subduction zones.
• Annobon — A volcanic island situated in the Atlantic Ocean, south of the equator, constituting a distinct province of Equatorial Guinea. Historically discovered by Portuguese navigators on New Year's Day in 1473, the isolated locality is recognized for its spectacular mountainous relief, its crater lake named Mazafin, and for preserving a unique local creole culture.
• Arequipa — A proper name designating the second-largest city in Peru and the capital of the province and region of the same name, situated at an altitude of over 2300 meters in the Andes Mountains. The city is globally recognized structurally as the 'White City' (Ciudad Blanca) due to its monumental historical buildings constructed from sillar, a white volcanic porous stone, with its historical center being declared a UNESCO World Heritage site.
• Augitite — An effusive, ultrabasic, and melanocratic igneous rock, completely lacking feldspars, composed primarily of large augite and magnetite crystals embedded in a glassy or microcrystalline basaltic groundmass. In structural geology, it represents a rare variety of volcanic pyroxenite.
• Auvergne — A mountainous historical and cultural region located in the Massif Central of central France; a former administrative province famous for its spectacular volcanic relief (Chaîne des Puys), its thermal springs, and medieval castles, currently integrated into the Auvergne-Rhône-Alpes region.
• Azores — A Portuguese archipelago composed of nine volcanic islands located in the middle of the North Atlantic Ocean, approximately 1500 km west of Lisbon; it represents an autonomous region of Portugal, world-renowned for its mountainous terrain, volcanic crater lakes, mild oceanic climate, and lush vegetation.