UNDERWATER GEOGRAPHICAL FEATURES & EXPLORATION - IN NEWS ( LAST 3 YRS )

UNDERWATER GEOGRAPHICAL FEATURES & EXPLORATION – CHRONOLOGICAL NOTES

19th CENTURY: EARLY SCIENTIFIC IDENTIFICATION

Hudson Canyon

• First scientifically identified in the 19th century by geologist Prof. J. D. Dana
• Recognized as the submerged channel of the Hudson River
• Located ~100 miles southeast of New York City in the Atlantic Ocean
• Represents one of the earliest examples of understanding submarine canyon systems

1874: DISCOVERY OF SUBMARINE RIDGE

Juan de Fuca Ridge

• First detected in 1874
• Discovered by USS Tuscarora, a U.S. Navy vessel commanded by George Belknap
• Identified during survey for undersea cable
• A submarine mountain range, indicating early exploration of mid-ocean ridges

1925: EXPLORATION PHASE

Hudson Canyon (Detailed Exploration)

• Brought to wider scientific attention in 1925
• Explored by naturalist William Beebe during the Arcturus Expedition
• Marked transition from identification to active marine exploration

HUDSON CANYON: GEOMORPHOLOGY & FEATURES

• A massive submarine canyon in the Atlantic Ocean
• Extends 350–400 miles from the continental shelf edge
• Depth reaches nearly 2.5 miles (~10,000 feet)
• Often called the “Grand Canyon of the Atlantic”
• Formed by Ice Age river systems
• Acts as a major marine habitat:
  • Sharks
  • Whales
  • Deep-sea corals

COMPARATIVE GEOGRAPHY

Hudson Canyon vs Grand Canyon

BAY OF BENGAL FEATURE

Swatch of No Ground (Ganga Trough)

• A submarine canyon located south of Ganges-Brahmaputra delta
• Also known as Ganga Trough
• Crosses the continental shelf diagonally
• Structure:
  • Flat floor width: 5–7 km
  • Wall inclination: ~12°
  • Depth at shelf edge: ~1200 m
• Extends further into Bay of Bengal as fan valleys with levees (~2000 km)
• Known for rich marine biodiversity

SUBMARINE VOLCANIC CHAINS & HOTSPOTS

Cobb–Eickelberg Seamount Chain

• Located in Northeast Pacific Ocean
• A linear chain of underwater volcanoes
• Formed by stationary Cobb hotspot
• Extends over 1000 miles:
  • From Aleutian Trench
  • To Juan de Fuca Ridge
• Demonstrates Pacific Plate movement (northwest direction)

Axial Seamount

• Youngest and most active volcano in the chain
• Located at southeastern end

RECENT VOLCANIC ACTIVITY (2022–2024)

Ruby Seamount

• Located in Mariana Arc (Pacific Ocean)
• Around 27 miles northwest of Saipan
• Depth: 175–230 meters below sea level
• Known for explosive eruptions
• Recorded eruptions:
  • 1966
  • 1995
  • September 2023 (detected via seismoacoustic signals & satellite plume)

Ahyi Seamount: ACTIVE UNDERWATER VOLCANO

Location & Context

• Located in Northern Mariana Islands (Western Pacific Ocean)
• Around:
  • 18 km southeast of Farallon de Pajaros (Uracas)
  • ~6115 km west of Honolulu
• Part of Mariana Volcanic Arc

Volcanic Activity Timeline

• Mid-October (2022): Seismic activity detected
• Evidence:
  • Seismo-acoustic signals
  • Satellite imagery showing water discoloration
• Scientists uncertain due to inaccessibility of deep ocean region

Recent Observations

• Associated with underwater eruption activity
• Studied by:
  • U.S. Geological Survey (USGS)
• Explored during:
  • 2025 Nautilus Expedition Season
• Region known for:
  • Volcanic peaks
  • Coral reef formations
  • Marine biodiversity

KEY SCIENTIFIC INSIGHTS

• Submarine canyons like Hudson Canyon and Swatch of No Ground reflect ancient river systems and sediment transport processes
• Mid-ocean ridges and seamount chains (e.g., Juan de Fuca Ridge, Cobb hotspot) indicate plate tectonics and mantle plume activity
• Active seamounts like Ahyi and Ruby highlight ongoing submarine volcanism
• Deep-sea regions serve as biodiversity hotspots and climate study zones

CORE TAKEAWAY (EXAM ORIENTED)

• Hudson Canyon → Largest Atlantic submarine canyon, Ice Age origin
• Swatch of No Ground → Bay of Bengal canyon linked to Ganga system
• Juan de Fuca Ridge → Early detected mid-ocean ridge (1874)
• Cobb Seamount Chain → Hotspot-driven volcanic chain
• Ahyi & Ruby Seamounts → Active submarine volcanism (recent activity)