Layer 0 looks global but its physical flow depends on a handful of narrow sea passages. Most of the raw material shipped across oceans each year, oil, iron ore, coal, grain, has to pass through straits that narrow to a few hundred metres in places. Closing one locks up Layer 1's manufacturing chains within days.
Petroleum liquids flow (million barrels/day) and the width of the narrowest point. World petroleum liquids output is 101 Mb/d, the bars are its share.
Strait of Malacca23,7 Mb/d
Narrowest: 3 km · The main route for Middle East oil plus Australian-Brazilian iron ore and coal to East Asia
Shallow water, dense traffic, piracy. If closed, a detour via Lombok/Sunda adds 1,600 km.
Alternative route: Lombok or Sunda Strait (+3-4 days)
Strait of Hormuz21,0 Mb/d
Narrowest: 33 km · About one fifth of global LNG
Military tension / closure. The Gulf's only sea outlet, no alternative; pipelines carry only a small share of capacity.
Alternative route: None (partial UAE and Saudi pipelines)
Suez Canal + SUMED9,2 Mb/d
Narrowest: 300 m · About 12-15% of world seaborne trade by volume, 30% of container traffic
Grounding (2021 Ever Given), regional conflict, missile threat. The Cape of Good Hope route adds 10 days for Asia-Europe.
Alternative route: Cape of Good Hope (+10 days, +6,000 nmi)
Bab el-Mandeb8,8 Mb/d
Narrowest: 29 km · The southern gate for everything to and from Suez
Regional conflict and attacks on ships can effectively divert the route to the Cape.
Alternative route: Cape of Good Hope (same detour as Suez)
Danish Straits3,3 Mb/d
Narrowest: 4 km · Crude and products leaving Russian Baltic ports
The Baltic's only natural outlet to the North Sea; shallow and narrow.
Alternative route: None (the Kiel Canal takes only small vessels)
Turkish Straits3,0 Mb/d
Narrowest: 700 m · The only sea outlet for Black Sea grain and fertiliser
The Bosphorus is 700 m at its narrowest; an accident or geopolitical blockade locks in the Black Sea.
Alternative route: None, the Black Sea is landlocked
Panama Canal1,0 Mb/d
Narrowest: 300 m · US grain exports, LPG and containers; about 5% of world seaborne trade
Water constraint: the 2023-2024 drought cut daily transits from 36 to 22. Climate is the canal's recurring bottleneck.
Alternative route: Strait of Magellan or a US land bridge by rail (+8-15 days)
Oil is not the whole story. The main dry bulk shipped by sea through the same passages each year (Gt):