erics like buckland because it allowed them to incorporate thebiblical flood of noah into serious scientific discussions。 uniformitarians by contrast believedthat changes on earth were gradual and that nearly all earth processes happened slowly； overimmense spans of time。 hutton was much more the father of the notion than lyell； but it waslyell most people read； and so he became in most people’s minds； then and now； the father ofmodern geological thought。
lyell believed that the earth’s shifts were uniform and steady—that everything that hadever happened in the past could be explained by events still going on today。 lyell and hisadherents didn’t just disdain catastrophism； they detested it。 catastrophists believed thatextinctions were part of a series in which animals were repeatedly wiped out and replacedwith new sets—a belief that the naturalist t。 h。 huxley mockingly likened to “a succession ofrubbers of whist； at the end of which the players upset the table and called for a new pack。” itwas too convenient a way to explain the unknown。 “never was there a dogma more calculatedto foster indolence； and to blunt the keen edge of curiosity；” sniffed lyell。
lyell’s oversights were not inconsiderable。 he failed to explain convincingly howmountain ranges were formed and overlooked glaciers as an agent of change。 he refused toaccept louis agassiz’s idea of ice ages—“the refrigeration of the globe；” as he dismissivelytermed it—and was confident that mammals “would be found in the oldest fossiliferousbeds。” he rejected the notion that animals and plants suffered sudden annihilations； andbelieved that all the principal animal groups—mammals； reptiles； fish； and so on—hadcoexisted since the dawn of time。 on all of these he would ultimately be proved wrong。
yet it would be nearly impossible to overstate lyell’s influence。 the principles of geologywent through twelve editions in lyell’s lifetime and contained notions that shaped geological thinking far into the twentieth century。 darwin took a first edition with him on thebeaglevoyage and wrote afterward that “the great merit of the principles was that it altered thewhole tone of one’s mind； and therefore that； when seeing a thing never seen by lyell； one yetsaw it partially through his eyes。” in short； he thought him nearly a god； as did many of hisgeneration。 it is a testament to the strength of lyell’s sway that in the 1980s when geologistshad to abandon just a part of it to acmodate the impact theory of extinctions； it nearlykilled them。 but that is another chapter。
meanwhile； geology had a great deal of sorting out to do； and not all of it went smoothly。
from the outset geologists tried to categorize rocks by the periods in which they were laiddown； but there were often bitter disagreements about where to put the dividing lines—nonemore so than a long…running debate that became known as the great devonian controversy。
the issue arose when the reverend adam sedgwick of cambridge claimed for the cambrianperiod a layer of rock that roderick murchison believed belonged rightly to the silurian。 thedispute raged for years and grew extremely heated。 “de la beche is a dirty dog；” murchisonwrote to a friend in a typical outburst。
some sense of the strength of feeling can be gained by glancing through the chapter titlesof martin j。 s。 rudwick’s excellent and somber account of the issue； the great devoniancontroversy。 these begin innocuously enough with headings such as “arenas of gentlemanlydebate” and “unraveling the greywacke；” but then proceed on to “the greywacke defendedand attacked；” “reproofs and recriminations；” “the spread of ugly rumors；” “weaverrecants his heresy；” “putting a provincial in his place；” and （in case there was any doubtthat this was war） “murchison opens the rhineland campaign。” the fight was finally settledin 1879 with the simple expedient of ing up with a new period； the ordovician； to beinserted between the two。
because the british were the most active in the early years； british names are predominantin the geological lexicon。 devonian is of course from the english county of devon。 cambrianes from the roman name for wales； while ordovician and silurian recall ancient welshtribes； the ordovices and silures。 but with the rise of geological prospecting elsewhere；names began to creep in from all over。jurassic refers to the jura mountains on the border offrance and switzerland。permian recalls the former russian province of perm in the uralmountains。 forcretaceous （from the latin for “chalk”） we are indebted to a belgian geologistwith the perky name of j。 j。 d’omalius d’halloy。
originally； geological history was divided into four spans of time： primary； secondary；tertiary； and quaternary。 the system was too neat to last； and soon geologists werecontributing additional divisions while eliminating others。 primary and secondary fell out ofuse altogether； while quaternary was discarded by some but kept by others。 today onlytertiary remains as a mon designation everywhere； even though it no longer represents athird period of anything。
lyell； in his principles； introduced additional units known as epochs or series to cover theperiod since the age of the dinosaurs； among them pleistocene （“most recent”）； pliocene（“more recent”）； miocene （“moderately recent”）； and the rather endearingly vague oligocene（“but a little recent”）。 lyell originally intended to employ “…synchronous” for his endings；giving us such crunchy designations as meiosynchronous and pleiosynchronous。 thereverend william whewell； an influential man； objected on etymological grounds andsuggested instead an “…eous” pattern； producing meioneous； pleioneous； and so on。 the “…cene” terminations were thus something of a promise。
nowadays； and speaking very generally； geological time is divided first into four greatchunks known as eras： precambrian； paleozoic （from the greek meaning “old life”）；mesozoic （“middle life”）； and cenozoic （“recent life”）。 these four eras are further dividedinto anywhere from a dozen to twenty subgroups； usually called periods though sometimesknown as systems。 most of these are also reasonably well known： cretaceous； jurassic；triassic； silurian； and so on。
1then e lyell’s epochs—the pleistocene； miocene； and so on—which apply only to themost recent （but paleontologically busy） sixty…five million years； and finally we have a massof finer subdivisions known as stages or ages。 most of these are named； nearly alwaysawkwardly； after places： illinoian； desmoinesian； croixian； kimmeridgian； and so on in likevein。 altogether； according to john mcphee； these number in the “tens of dozens。”
fortunately； unless you take up geology as a career； you are unlikely ever to hear any of themagain。
further confusing the matter is that the stages or ages in north america have differentnames from the stages in europe and often only roughly intersect in time。 thus the northamerican cincinnatian stage mostly corresponds with the ashgillian stage in europe； plus atiny bit of the slightly earlier caradocian stage。
also； all this changes from textbook to textbook and from person to person； so that someauthorities describe seven recent epochs； while others are content with four。 in some books；too； you will find the tertiary and quaternary taken out and replaced by periods of differentlengths called the palaeogene and neogene。 others divide the precambrian into two eras； thevery ancient archean and the more recent proterozoic。 sometimes too you will see the termphanerozoic used to describe the span enpassing the cenozoic； mesozoic； and paleozoiceras。
moreover； all this applies only to units of time 。 rocks are divided into quite separate unitsknown as systems； series； and stages。 a distinction is also made between late and early（referring to time） and upper and lower （referring to layers of rock）。 it can all get terriblyconfusing to nonspecialists； but to a geologist these can be matters of passion。 “i have seengrown men glow incandescent with rage over this metaphorical millisecond in life’s history；”
the british paleontologist richard fortey has written with regard to a long…running twentieth…century dispute over where the boundary lies between the cambrian and ordovician。
at least today we can bring some sophisticated dating techniques to the table。 for most ofthe nineteenth century geologists could draw on nothing more than the most hopefulguesswork。 the frustrating position then was that although they could place the various rocksand fossils in order by age； they had no idea how long any of those ages were。 whenbuckland speculated on the antiquity of an ichthyosaurus skeleton he could do no better thansuggest that it had lived somewhere between “ten thousand； or more than ten thousand timesten thousand” years earlier。
although there was no reliable way of dating periods； there was no shortage of peoplewilling to try。 the most well known early attempt was in 1650 when archbishop jamesussher of the church of ireland made a careful study of the bible and other historical sourcesand concluded； in a hefty tome called annals of the old testament ； that the earth had been1there will be no testing h