Type

Inland Sea

Location

Entirely within Republic of Turkey (transcontinental Europe & Asia)

Area

Approximately 11,350 sq.km

Length

About 280 km

Maximum Width

Around 80 km

Average Depth

About 494 meters

Maximum Depth

Approximately 1,370 meters (deepest point in central trench)

Connecting Straits

Connected to Black Sea via Bosphorus Strait (northeast)
Connected to Aegean Sea via Dardanelles Strait (southwest)

Geological Importance

Lies directly on North Anatolian Fault a major strike-slip fault line responsible for severe seismic activity

Seismic Activity

Highly earthquake-prone; historical quakes include 1509, 1766, 1999 İzmit (magnitude 7.4) & 2025 Istanbul quake (magnitude 6.2)

Tectonic Setting

Transitional boundary between Anatolian Plate & Eurasian Plate

Climate

Humid Subtropical Climate (Cfa, Köppen classification)
Summers Hot & humid
Winters Cold & wet

Salinity Characteristics

Surface Freshwater dominated from Black Sea inflow
Bottom More saline due to Mediterranean inflow via Dardanelles
Leads to strong salinity stratification

Ecological Significance

Important for fish migration routes especially anchovy & mackerel; diverse marine ecosystems but facing threats from pollution & eutrophication

Major Islands

Marmara Island (largest, rich in marble)
Avşa Island
Paşalimani Island
Imrali Island (prison island)
Ekinlik Island
Prince Islands (cluster near Istanbul: Büyükada, Heybeliada etc.)

Major Coastal Cities

Istanbul (northeastern shore)
İzmit (eastern shore)
Yalova (eastern shore)
Bursa (south)
Tekirdağ (northwest)
Balıkesir (south)
Çanakkale (southwest near Dardanelles)

Historical Significance

Major maritime route during Roman, Byzantine & Ottoman times
Integral to control of Constantinople (Istanbul)
Key role in regional trade & defense

Economic Activities

Heavy shipping & port activities (especially at Istanbul & İzmit)
Fishing industry (decreasing due to pollution)
Tourism (Prince Islands, coastal resorts)
Marble extraction (Marmara Island)

Environmental Threats

Marine mucilage crisis (2021) due to eutrophication & pollution
Oil spills, industrial pollution from nearby cities
Overfishing & habitat degradation

Strategic Importance

Forms part of only maritime passage between Black Sea & Mediterranean (critical for global naval & shipping movements)

Natural Hazards

High tsunami risk due to fault movements beneath sea

Unique Feature

One of few inland seas that entirely separates a single country's European & Asian parts

Major Tectonic Plates

1. Anatolian Plate (microplate)
2. Eurasian Plate
3. Arabian Plate
4. African Plate

Minor/Associated Plates

Aegean Sea Plate (small plate near Greece)
Hellenic Plate (around Crete & southern Greece)

Movement of Anatolian Plate

Westward slip (~21–25 mm/year)
Squeezed between Arabian Plate (pushing northward) & Eurasian Plate (stationary to north)

Plate Boundary Types

Convergent Boundaries (Arabian Plate colliding with Eurasian Plate)
Transform Boundaries (strike-slip e.g. North Anatolian Fault)
Subduction Zones (African Plate subducting under Aegean/Anatolian region)

Major Fault Systems

North Anatolian Fault (NAF) A major east-west strike-slip fault extending ~1,500 km across northern Turkey.
East Anatolian Fault (EAF) A major strike-slip fault between Anatolian & Arabian Plates in eastern Turkey.
Hellenic Arc Subduction Zone African Plate subducts beneath Aegean & Anatolian plates.

North Anatolian Fault Details

Runs from eastern Turkey (Karlıova Triple Junction) to Marmara Sea & northern Aegean
Major cause of catastrophic earthquakes (e.g. 1939 Erzincan, 1999 İzmit)
Expected to produce large earthquakes near Istanbul

East Anatolian Fault Details

Left-lateral strike-slip fault
Site of devastating 2023 Turkey-Syria earthquakes (magnitude 7.8)

African Plate Subduction

South of Turkey
Subduction along Hellenic Trench & Cyprus Arc
Responsible for deep-seated earthquakes in southwestern Turkey

Seismic Hotspots

Istanbul (near NAF)
Eastern Turkey (EAF region)
Aegean coast & offshore islands (due to subduction & extension zones)
Southeastern Turkey (Arabian-Eurasian collision)

Tectonic Evolution

Result of collision between African-Arabian Plates & Eurasian Plate since late Mesozoic-Cenozoic periods
Formation of Taurus Mountains & complex fault networks

Triple Junctions

Karlıova Triple Junction (where North Anatolian, East Anatolian & Bitlis-Zagros faults meet)

Key Earthquakes in History

1509 Constantinople earthquake ("Little Doomsday")
1939 Erzincan earthquake (M 7.8)
1999 İzmit earthquake (M 7.4)
2020 Aegean Sea earthquake (M 7.0)
2023 Kahramanmaraş earthquakes (M 7.8 & M 7.5)

Earthquake Preparedness

Massive urban renewal projects post-1999 İzmit quake
Strengthening of infrastructure in Istanbul & other cities
Early warning systems being developed but many older buildings remain vulnerable

Potential Future Risk Zones

Marmara Sea (near Istanbul) - highest risk
Eastern Anatolia (continuing aftershocks post-2023)
Aegean coastal & offshore regions

Special Features

Turkey is one of most seismically active regions in world outside of major subduction zones.
The NAF is similar in behavior to San Andreas Fault in California (both are large strike-slip faults).

PRACTICE QUESTION

Q. Discuss tectonic setting of Turkey with reference to Anatolian Plate. How have major fault systems like North Anatolian Fault & East Anatolian Fault contributed to Turkey high seismic risk? Evaluate measures taken by Turkey to mitigate earthquake impacts.