In what are called geosynclines, or earth sags, the great beds of strata are accumulated. They are the dirt washed from highlands into midland seas. They are strata of sandstone, mudstone, or limestone; thin films in comparison with the fire-made earth crust. It was the wrinkling of basin fills by expansion or end push that built Himalaya and Appalachia. The mountains are etched out of foldings and overthrusts and faults by rotting and water transport. Pressing the strata endways to wrinkle them is called mountain building, much better named strata wrinkling. The thickest of them reached twelve miles vertically, but what is that to the earth’s crust of 1,800 miles? The crust lifts and lowers fault blocks. The little strata basins expand with heat on their bottoms and get pulled and pushed by underground lava intrusions. Also they get squeezed by global contraction between crust blocks, and shoved up and down by the agelong wobbles. The biggest wobble was the downdrop of the great oceans over fault blocks when the crust first cracked and settled over the core. Those oceans have shifted and adjusted in waves of global action ever since. The crust has kept the earth a sphere while lavas erupted and weighted down the blocks. This block wobble extends into the innermost continents. Eruptions up the cracks migrated from the continental seas to the shores of the present oceans. They changed composition as they did so, because they changed from under-air eruptions to under-sea eruptions, fifteen pounds pressure to 600 atmospheres pressure. From erosion eruptions with enormous heat, to deep sea eruptions with enormous chilling and pressure. And the latter are the volcanoes of the present day, mostly concealed except for the islands and sea borders. Meantime, the crust blocks continue to wobble up and down, and quakes continue to creak under the rock tides of sun and moon pulls. The creaks and wobbles are our big earthquakes, tidal waves, and eruptions. Such big accumulations of eruptions as the Cordillera or the Hawaiian Ridge is a terrific weight in a few million years. Both heaps have been at it since Miocene time, or for about 18 million years, banging down through the crust blocks on top of the core. Whether such balancing of heavy weights on top of the crust blocks is due to change of lava weights or sediment basins, six to twelve miles of rock vertically, the down squeeze and underflow is called by the Greek word isostasy. It means standing level and is a poor word because the earth’s crust never stands still. The blocks are eternally adjusting and creaking over a fluid core, the globe is whirling, the sun and moon are pulling, the volcanoes are erupting, and the solar system is shooting through space. Terra firma is never static. And our little atmospheric lives on top of it never stand still. We are hot, and we ourselves do a great deal of eroding.