ensity. t be uff inside. e kno togenerate our magnetic field some be a concentrated belt ofmetallic elements in a liquid state. t muc everyt—eract, o bet any time in ture—is a matter of at least some uncertainty, and generallyquite a lot of uncertainty.

    Even t of it , is a matter of some fairly strident debate.

    Nearly all geology texts tell you t continental crust is to six miles t ty-five miles tinents, and forty to sixty miles tain c ties ions. t beneatains, for instance, is only aboutnineteen to ty-five miles to quicksand. (Some people tailed picture of terior, o 40 km (25 mi) is t. From 40 to 400 km (25 to 250 mi) is tle. From 400 to 650 km (250 to 400 mi) is a transition zone betle.

    From 650 to 2,700 km (400 to 1,700 mi) is tle. From 2,700 to 2,890 km (1,700 to 1,900 mi) is t;Dquot; layer. From 2,890 to 5,150 km (1,900 to 3,200 mi) is ter core, and from 5,150 to 6,378 km (3,200 to3,967 mi) is the inner core.

    its crust are questions t divide geologists into t ly early in tory and t er. Strengtters. Ricrong of Yale proposed an early-burst t t of ing t agree  slybefore  at ics in a polemic in an Australian eart cuating myto a report inEarth magazine in 1998.

    “ter man,” reported a colleague.

    t and part of ter mantle togetone”), s on top of a layer of softer rock called t strengt sucerms are neverentirely satisfactory. to say t ts on top of ts adegree of easy buoyancy t isn’t quite rig is misleading to terials flo only in t glass is.