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Origins: How The Earh Made Us

Lewis Dartnell

More books on Evolution

Tibet is sometimes called the 'Third Pole' bc its tens of thousands of glaciers hold the largest store of ice outside Antarctica and the Arctic. These provide headwaters for the 10 biggest rivers in SE Asia - Yellow River, the Yangtse, Mekong, Indus. All these great rivers carry huge amounts of eroded sediment to fertilise the flood plains.

By 2030 China is forecast to have only 75% of water it needs, so control of Tibet is no small matter.

In the middle of the North Sea, between England and Denmark, lies the Dogger Bank, a huge sandbank that originated as the terminal moraine of the Scandinavian ice sheet during the last glacial phase. When sea levels were lower it was dry land and prime hunting ground. Today its shallow waters provide productive fishing for cod and herring.

The Dogger Bank ("dogger" is a Dutch word for trawler) helped lauch open sea navigation in Europe around AD 1000. With increased competition, fihers were drawn further and further out into the North Atlantic, first for cod, and then for whales.

The shallow Dogger Bank offered the potential for the Dutch to drain and reclaim land. But the building of dykes and windmills was expensive, and the only way to do it was for the whole community to invest and then share profits. These bond markets then gave rise to credit markets for investment in ship voyages. This is turn lead to futures markets as boat owners promised to sell a certain quantity of fish for a fixed price in a year's time. These derivatives could then be bought and sold like actual products.

The mediterranean is the last remnant of the prehistoric Tethys Ocean. In prehistory, the (Western) Med had dried up many times, laying down salt layers up to 2 km thick.

The African coastline is relatively smooth and bereft of natural harbours bc the African plate is tipping downwards and subducting under the Eurasian plate. The northern side of the Med, in contrast, is a drowned landscape of intricate bays, capes, harbours and little islands. So the northern rim has produced an endless stream of maritime cultures.

One type of marble, travertine, is formed at the mouth of hot springs when calcium carbonate precipitates out of solution to form limestone layers. Pressure underground transforms it to travertine. But most limestone is formed as a slimy mud of calcium carbonate from the shells of tiny sea creatures.

Copper is deposited in high concentrations at mid-ocean spreading ridges. Seawater trickles down to the magma, gets superheated and is forced back up through the crust, leaching minerals as it goes. When it hits the frigid ocean water, minerals precipitate out and are deposited close to the ridge. On rare occasions, these deposits get squeezed up between colliding plates. The Troodos mts in Cyprus is best eg in world of an ophiolite - a slice of what was once a spreading ridge in the Tethys Sea 50m years ago. Offers fabulously enriched ores - ores that are 20 per cent copper.

Cyprus is squeezed up by the African plate subducting beneath Eurasia. Great benefit to Minoan civilization in that copper funded its trading empire. But there is a downside to living on the edge of a subduction zone - bt 1600 and 1500 BC Thera blew - one of the most violent eruptions in history.

Series of barbarian incursions from the steppes. Their cavalry ran rings round static armies. But basic problem - horses need pasture. And agricultural societies produce lots of grain which nourishes people, but not horses. So raiders either had to hit and run, or else stay and settle down.

Genghis Khan and Mongols devastated the area, but the unification of Asia led to a century of booming trade - Pax Mongolica. They enforced peace, and kept taxes low, realizing they cd make more money from trade than from raiding booty. But as usual, there was a flip side - Black Death travelled with the traders.

From the nid-16th century the Military Revn turned balance of power against the steppe dwellers. Agrarian societies learned how to effectively use gunpowder for musket and cannon, coordinated army drills and far-reaching logistics to keep troops supplied. Above all, their economies were transforming with trade and industry, affording bigger and better equipped armies/

Coal is essentially a combustible sedimentary rock - fossilised sunshine. Coal dug up contains impurities such as sulphur. Coking (heating coal without letting it caych fire) drives out the impurities to produce a hotter-burning fuel.

The most massive and widespread coal deposits were created in the Carboniferous, a 60 million year period that ended about 300 million years ago. About 90% of the coal we burn comes from this period.

Normally, when a tree dies, it decompose; rots away, and there's nothing left to turn into coal. But in the Carboniferous, something happened to block that decomposition. Trees died but didn't rot. They were deposited in hot, nuggy swamps, but such conditions have prevailed many times without preventing decomposition. One suggestion was that the trees had developed lignin, and that Carboniferous fungi hadn't yet evolved to digest that. But turns out that (a) most of coal producing plants didn't have lignin, and (b) fungi evolve very quickly to exploit any new food source.

Author suggests geological reason - seas constantly flooded forests bc Carboniferous was a time of violent upheaval - the Variscan Orogeny - which not only pushed up mts such as the Appalachians, but also created basins which dropped as the mts stretched up.

While coal is formed by the compacting and baking of ancient forests, oil and natural gas are formed from the remains of microscopic marine plankton. Most of today's oil was formed in the ancient Tethys Sea in two pulses 155 and 100 million years ago. Again, the normal process is that sea floor bacteria consume dead plankton that drifts down. To make lots of oil need warm shallow seas to produce lots of plankton, and need the sea floor to be oxygen depleted so no bacteria. This happened in the Cretaceous when climate hotter, so more water/seas, and the poles melted, shutting off the global conveyor belt that mixes cold and warm water.

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