Nancy Smith asks,
"I was wondering if anyone knew of a general book on ammonites?  Nothing
particular to regions or species or periods, just a basics kind of
all-around information book."

The best general book I know of is "The Ammonites," by Lehmann. This book
summarizes what was known about their behavior, habitats, and so on, as of
about ten years ago. Sorry for the brief citation, but I don't have time to
visit the library today.

Andrew K. Rindsberg
Geological Survey of Alabama

P.S. Art Weil's question about changes in the height of the Mid-Atlantic
Ridge affecting sealevel was an astute one, and was handled very nicely by
other people. But thanks anyway for the plug, Art.

As to oil extraction lowering ground elevations, this used to happen
occasionally in cases where the petroleum was in pores in relatively
shallowly buried sediments. While the petroleum was in the pores, it helped
to hold the grains of sediment (i.e, sand, silt, gravel) up against the
considerable pressure, in the same way that water can hold up two people and
a cat on a water bed against their considerable weight. This pressure is not
original, but increases over time in sedimentary basins as more sediment is
laid down. Residents of California will be familiar with this concept if
they live on basins such as those of San Francisco Bay, the Great Valley, or
greater Los Angeles, since these basins are relatively young and are still
shaped like "basins."

Anyway, if you remove the water from a water bed, the overlying sheets and
blankets will sink. And when petroleum is pumped out without replacing it
with other fluids, the grains also shift and the pores collapse, no longer
held up against the pressure of overlying rock strata. When zillions of
little pores collapse, that can add up to a big drop in ground elevation,
say, 10 or 20 feet. This is enough to make streams flow backward from the
sea (San Jose, California), force abandonment of a coastal suburb awash at
high tide (Baytown, Texas), or require levees against the high tide (naval
facilities at Long Beach, California). Nowadays, in these situations the oil
companies pump water (usually salty groundwater) into nearby wells while
pumping oil out of other wells. This "flooding" process actually helps to
drive more oil out of the pores than would come out otherwise, so it's a
win-win situation.