Daily Archives: November 22, 2007

Global Warming, the Blog Epic ~ 07 ~ Sea Level Change

This is the seventh in a series of reposts from gregladen.com on global warming. i-e1372cd57ce206dff3631a4a9438e737-epic-GlobalWarming.jpgThis installment is about sea level rise and fall, in the past. Sea level change that results from the formation and melting of glaciers not only has an enormous impact on the physical nature of the landscape, but it also would not have gone unnoticed by people living ever pretty far from the sea!With large amounts of the world’s water trapped in glaciers (mainly continental glaciers), the sea level drops. When that ice melts, the sea level rises.As you know, the earth is covered by two kinds of surface: Continents, which are relatively tall and buoyant and which have a tendency to move around, and sea floor, which is structurally different from the continents. But if you look at the oceans, you will see that they cover both sea floor and parts of the continents. The parts of the continents that are covered by sea floor are typically referred to as “continental shelf.” All this … this continental shelf … really is the edge of the continents themselves that happen at the moment to be covered with the sea. There are places, like the coast of California, where there is no shelf, and other places, like the coast of New England, much of the Caribbean and large parts of the Gulf of Mexico, that have extensive shelf. If you removed all the water from this shelf, you could fit a couple of more New England states between Boston (now on the coast) and the new coast line. Continue reading Global Warming, the Blog Epic ~ 07 ~ Sea Level Change

The Three Necessary and Sufficient Conditions of Natural Selection

Natural Selection is the key creative force in evolution. Natural selection, together with specific histories of populations (species) and adaptations, is responsible for the design of organisms. Most people have some idea of what Natural Selection is. However, it is easy to make conceptual errors when thinking about this important force of nature. One way to improve how we think about a concept like this is to carefully exam its formal definition. Continue reading The Three Necessary and Sufficient Conditions of Natural Selection