Harrat

Harrat
Name	Harrat
Type	Volcanic field
Location	Arabian Peninsula, Northwest Africa
Area	Variable (thousands of km²)
Last eruption	Holocene in some fields
Geology	Basaltic lava fields, cinder cones, shield volcanoes

Harrat

Harrat are extensive basaltic volcanic fields found across the Arabian Peninsula and Northwest Africa whose landscapes include lava flows, cinder cones, and shield volcanoes. These volcanic fields occur in proximity to tectonic features such as the Red Sea Rift, Gulf of Aden rift, and the East African Rift, and are studied in relation to plate-boundary processes involving the Arabian Plate, African Plate, and Eurasian Plate. Geologists, volcanologists, and regional archaeologists investigate Harrat to understand flood basalt volcanism, magmatic plumbing, and prehistoric human use of volcanic terrains.

Etymology and Definition

The term Harrat derives from Classical and local Arabic cartography and toponymy used in historical sources including maps created during the eras of the Ottoman Empire, the Caliphate, and later colonial surveys by British Empire officers and explorers. In scientific literature produced by institutions such as the U.S. Geological Survey and national geological surveys of Saudi Arabia and Jordan, Harrat denotes continental basaltic fields characterized by monogenetic and polygenetic volcanic cones, extensive ʻaʻā and pāhoehoe-type flows, and scattered maars. Usage appears in regional studies authored by researchers from universities such as King Saud University, University of Oxford, and University of Cambridge and in reports from international bodies like UNESCO when Harrat landscapes intersect cultural heritage.

Geology and Formation

Harrat volcanic fields are predominantly alkali olivine basalt systems formed in intraplate settings influenced by lithospheric extension. Magmatism has been linked to mantle upwelling and hotspot-like thermal anomalies proposed in models by researchers at MIT, Stanford University, and ETH Zurich. Tectonic drivers include rifting associated with the opening of the Red Sea, transtensional faulting along the Dead Sea Transform, and interactions with the Afro-Arabian Shield. Petrogenetic studies cite partial melting of subcontinental lithospheric mantle and metasomatized mantle sources identified in geochemical analyses conducted at facilities such as the Geological Survey of Saudi Arabia and laboratories at Caltech.

Distribution and Major Harrats

Major volcanic fields occur in western and northern Saudi Arabia, southern Syria, northern Jordan, and parts of Morocco and Algeria. Notable named fields include those mapped and described in regional atlases: fields adjacent to Medina, near Tabuk, around Al-Ula, and the large basalts north of Madinah. In northwest Africa, analogous basaltic expanses occur near Rabat and in the Atlas Mountains foothills. Cartographic and remote sensing work by agencies like NASA and the European Space Agency has aided in delineating the areal extent, while geological mapping by the Saudi Geological Survey and national ministries has produced inventories of cones and lava flow units.

Volcanic Features and Petrology

Harrat volcanic fields host morphological features typical of flood basalt provinces including small shield volcanoes, scoria cones, lava tubes, and rootless cones documented in fieldwork by teams from King Abdulaziz University and international collaborations with University of Texas at Austin. Petrologic studies identify minerals such as olivine, clinopyroxene, and plagioclase in basalts analyzed at laboratories including Birkbeck, University of London and University of Oslo. Geochemical signatures range from tholeiitic to alkaline basalts, with trace-element patterns that researchers from Leeds University and Charles University interpret as reflecting variable degrees of partial melting and mantle source enrichment.

Geological History and Chronology

Chronological frameworks for individual Harrat units rely on radiometric dating methods such as K–Ar and 40Ar/39Ar analyses performed in isotope geochemistry facilities at ANU and GFZ Potsdam. Volcanic activity spans from the Neogene through the Quaternary, with some eruptions documented in the Holocene by archaeologists and geomorphologists from institutions like University of Copenhagen and Max Planck Institute for Chemistry. Stratigraphic correlations incorporate paleoclimatic records from nearby sedimentary basins studied by researchers at Columbia University and University of California, Berkeley to relate eruptive phases to regional environmental change.

Human Interaction and Cultural Significance

Harrat landscapes intersect trade routes, pilgrimage paths to Mecca, and archaeological sites tied to cultures documented by scholars at British Museum and National Museum of Saudi Arabia. Rock art, lithic scatters, and ancient habitation sites studied by archaeologists from University of York and University of Lyon indicate human use of volcanic terrains for raw materials and refuge. Historical narratives by chroniclers in the Umayyad Caliphate and travelers such as Ibn Battuta reference stark volcanic landscapes, while modern tourism initiatives by national tourism authorities in Saudi Arabia and Jordanian Department of Antiquities highlight volcanic scenery and heritage conservation.

Hazards and Monitoring

Although many Harrat fields are dormant, some host recorded Holocene eruptions and pose hazards assessed by regional observatories including the Saudi Geological Survey, Jordanian Seismological Observatory, and global monitoring networks like the Global Seismographic Network. Hazard analyses use seismicity, satellite-based thermal anomaly detection by NOAA and Copernicus, and geodetic monitoring via GPS campaigns organized by research groups at Imperial College London and University of Hawaiʻi at Mānoa. Civil protection agencies coordinate preparedness planning for lava flow, gas emissions, and volcanic earthquakes in collaboration with emergency management organizations such as Civil Defence units in affected countries.

Category:Volcanic fields