History of the North Sea great herring fishing industry resulting in Scotland becoming a European leader in that industry. During the First Schleswig War (1848–51), the Crimean War (1854–56) and the Second Schleswig War (1864), belligerents took steps to reduce or eliminate commerce in the North Sea by their enemies. In the first Schleswig War, Denmark was able to halt maritime commerce by Germany in the North Sea and in the second, imposed tolls on ships crossing through the Danish straits between the Baltic and North Seas. The Crimean War saw British and French expeditions sent into the Baltic to prevent Russian ships' egress into
Opening of the North Atlantic Ocean American plates. The ages of the earliest volcanic rocks from this plume lie in the late Paleocene, and both sides of the Atlantic Ocean contain these rocks. Since these rocks have been dated to the late Paleocene, this lines up with the time of breakup of the North Atlantic continent, so some think it could have been a contributing factor. This theory views volcanism as the resultant of lithospheric processes rather than heat from the mantle rising up. Instead of heat coming up from deep in the mantle, volcanic anomalies come from a shallow source. Volcanism thus occurs where the