Kolbert in chapter 4 discusses ammonites and why they are dying out. The Hill Town of Gubbio near the edge of town has narrow gorge known as Gola del Bottaccione which Walter Alvarez in the 1970s discovered a giant asteroid that ended the Cretaceous period. Alvarez believed extinction was a gradual process. Alvarez noticed forams seemed to disappear quickly an abrupt process. Walter’s father, Luis Alvarez, came up with the idea of clocking the clay using iridium. Iridium can be easily preserved and very common in meteorites. When the samples were analyzed from Danish to South Island of New Zealand iridium was off the charts. This allowed for the Alvarezes’ theory which discusses how an asteroid collided with earth and upon impact released energy allowing huge amounts of iridium to spread across the world. However, many paleontologists criticized Alvarez's theory believing that it was “slow extermination.”
Alvarezes’ main cause of the K-T extinction was the dust created by the impact.The dust caused by the asteroid increased temperature levels killing off plants as photosynthesis was blocked, the heat wave that ensued would lead to a “impact winter” which forests died off and collapsed marine ecosystems. Ammonites couldn’t survive as ocean surface became toxic. The theme revolving this chapter is environmental problems because ammonites were fit for their current environment. Unlike popular belief ammonites were doing fine during the Createaous period they could withstand many conditions as,“The walls between the chambers, known as septa, were fantastically elaborate folded into intricate ruffles...This evolutionary development allowed ammonites to build shells that were at once light and robust-capable of withstanding many atmospheres' worth of water pressure,”(84) indicating how ammonites could sustain such harsh conditions. The impact of the asteroid showed even advantageous traits are lethal to survival.
Hever Castle (London)
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