last glacial period milankovitch cycles last glacial maximum quaternary glaciation mammoth steppe laurentide ice sheet wisconsin glaciation late cenozoic ice age late antique little ice age würm glaciation late paleozoic icehouse 100,000-year problem last glacial maximum refugia sturtian glaciation cordilleran ice sheet mid- pleistocene transition andean- saharan glaciation late ordovician glaciation penultimate glacial period illinoian (stage) saale glaciation baykonurian glaciation vashon glaciation riss glaciation anglian stage pre- illinoian gaskiers glaciation kansan glaciation cromerian stage the world in winter irish sea glacier glacial relict elster glaciation wolstonian stage
History_Historical eras