Norse and Aztecs quiz: 8 questions

The warmth did not extend everywhere. Mann and colleagues found a relatively warm North Atlantic alongside cooler parts of the tropical Pacific. That regional pattern helps explain why the effects differed from coast to coast.

The overlapping riveted planks formed a light hull that could flex with the waves. Drawing only about a metre of water, a ship could cross open sea, row up rivers and land on beaches. Its wool sail, meanwhile, required years of women’s labour.

A burst of cosmic radiation left a radiocarbon spike in the tree ring formed in 993. Kuitems’s team found the marker in three cut pieces of wood and counted 29 rings from it to the bark. The trees were therefore felled in 1021.

Arneborg’s studies indicate that marine protein rose from about 15–50 percent at settlement to 50–80 percent by the end. Seal remains dominate rubbish heaps and are abundant at farms. The Norse adapted to local food sources far more than the old stereotype suggests.

Stockfish was cod air-dried at Lofoten and shipped through Bergen. It kept for years without salt and reached markets in England and the Hanseatic towns. Cod thrived in the cold, so the trade survived the climate that helped end Norse Greenland.

The basin had no outlet, so water left by evaporation and salts accumulated in its lowest lake. Springs fed the southern lakes, keeping them fresh. The great chinampa zone lay in this southern area.

Painted symbols and Spanish notes identify towns and goods owed to the Triple Alliance by 38 provinces, including grain, cotton cloth, cacao and feathers. Historians debate whether some symbols represent single items or loads of twenty, as well as how frequently payments were made.

The gaps let water pass between parts of the lake, while removable bridges allowed defenders to cut access to the city. During the retreat of June 1520 and the siege of 1521, those same gaps became deadly obstacles.