Term: Gravel
**Definition and Properties of Gravel**:
– Gravel is a loose aggregation of rock fragments.
– Classified by particle size range, from granule- to boulder-sized fragments.
– Different bulk densities and hydraulic conductivity levels.
– Sometimes distinguished from rubble, which is angular in shape.
– Various scales define gravel based on particle sizes.
**Origin and Distribution of Gravel**:
– Derived from the disintegration of bedrock as it weathers.
– Most common mineral found in gravel is quartz.
– Deposited in various settings like stream channels, alluvial fans, and marine environments.
– Widely distributed, mainly as river deposits and glacial deposits.
– Wind-formed gravel megaripples in Argentina have similarities to those on Mars.
**Production and Uses of Gravel**:
– Major raw material in construction industry.
– Sand and gravel production in the U.S. constituted 23% of industrial mineral production in 2020.
– Almost half of construction sand and gravel used as aggregate for concrete.
– Crushed stone is displacing natural gravel in some regions.
– Types include bank gravel, bench gravel, crushed stone, fine gravel, and pay gravel.
**Geological Aspects of Gravel**:
– Sediments with over 30% gravel become conglomerate rock.
– Conglomerates found in sedimentary rock, usually
Gravel (/ˈɡrævəl/) is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentary and erosive geological processes; it is also produced in large quantities commercially as crushed stone.
Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular gravel (2–4 mm or 0.079–0.157 in) and pebble gravel (4–64 mm or 0.2–2.5 in). ISO 14688 grades gravels as fine, medium, and coarse, with ranges 2–6.3 mm (0.079–0.248 in) for fine and 20–63 mm (0.79–2.48 in) for coarse. One cubic metre of gravel typically weighs about 1,800 kg (4,000 lb), or one cubic yard weighs about 3,000 lb (1,400 kg).
Gravel is an important commercial product, with a number of applications. Almost half of all gravel production is used as aggregate for concrete. Much of the rest is used for road construction, either in the road base or as the road surface (with or without asphalt or other binders.) Naturally occurring porous gravel deposits have a high hydraulic conductivity, making them important aquifers.