GEOL 1109 Topic 2- The Historical Beginnings of Geology

when did people start to question rocks

paradigms

everyday ideas or ways of thinking it also depends on what we and others think

religion, natural theology, theoretical geology

the way people explain different aspects of the natural world (stars, planets, moons, floods etc)

geocentric universe

600 BC Greek philosophers debated about the structure of the universe. in original ideas the earth was at the centre of the universe this model is known as the geocentric universe

all celestial bodies and related features lie within what?

the globe of stars

what did Pythagoreans suggest in 6th century BC?

they suggested that the earth was round because of the shadow that it casts on the moon during Lunar eclipses

Herodotus (484-425 BC)

5th century BC. he was aware that earthquakes caused a large scale shattering and shaped the landscape. He also observed that the sediment carried along the Nile was what created its delta

Eratosthenes (276-194 BC)

almost accurately measured the earths diameter by using the position of the sun in 2 different places.

Natural History

written by Pliny the Elder (roman) in 77 AD

how did sea creatures become encased in stone? (2 hypothesis)

1st hypothesis- fossils fall from the sky during thunderstorms, they associate this as bad so fossils are evil.

2nd hypothesis- fossils are the remains of animals

Mount Etna eruption of 1669

lava from the eruption spread 40 square km across the landscape no casualties

Lisbon earthquake 1775

almost completely destroyed the city of Lisbon. 7.7 or greater magnitude

heliocentric

the sun is at the centre of the universe

The Sacred Theory of the Earth

By Thomas Burnet who attempted to reconcile an imperfect world with genesis. using his model he argued that the earth was smooth and spherical and composed of core heavy particles that were surrounded by shells of liquid and air

what was the liquid in Burnet’s model

it consisted of fat and oily liquid in the upper half and water in the lower half

what was the dust in Burnet’s model

it came from the primeval atmosphere and settled within oily shells that became firm and habitable land

Great Deluge

occurred when solid shells collapsed into the waters below and gushed out to flood the earth

Nicolas Steno

Born on Jan 11, 1638 in Copenhagen, Denmark. He and James Hutton are the fathers of modern geology

what was stenos geological theory question? and how did he describe crystals?

how does a solid like a shell or crystal become enclosed within another solid? steno reasoned that the enclosed body also has to be a solid before the enclosing rock/mineral solidified. he described crystals, outlined their growth and recognized the angles between crystal faces that are constant regardless or size or shape

principle of superposition (steno)

oldest strata lie at the bottom of a stratigraphic succession, youngest rocks are found at the top of a stratigraphic succession

principles of original horizontality and continuity (steno)

all rocks were originally deposited horizontally under the action of gravity and continue laterally in all directions

principles of inclusions (steno)

all rock fragments are found within a stratigraphic layer must be older than the stratigraphic layer itself

principle of cross-cutting relationships (steno)

the geological feature that cuts across another geological feature is the younger of the two features

Recap of steno

all of his ideas helped reshape the way society thought about the order various rock units formed and the framework for relative age determination was created

rock and fossil collections

starting at the Renaissance people everywhere began to think more scientifically. educated people collected fossils and minerals. “Geologizing” became popular for all classes. there was still some uncertainty about these ideas and people would explain them in terms of the great flood or the Noachian deluge

what did Lehmann and Werner recognize (they were deluge supporters)

they recognized that the oldest rocks were in the high peaks of the Alps next came the rocks that dipped off the peaks next the flat lying strata and next the alluvial. these represented the 4 events that forming earths crust with the flat and alluvial coming after the flood

Catastrophism (Georges Cuvier 1769-1832)

a hypothesis that states that earths history can be explained by a series of supernaturally derived catastrophes (specifically floods). this was a popular hypothesis. George Cuvier was the first person to propose the phenomenon of extinction in 1796

Law of Faunal Succession

George Cuvier recognized that fossil-bearing strata represented successive assemblages of organism.

Uniformitarianism

present geological processes have been operating throughout earths history and can be used to explain past processes.

James Hutton (1726-1797)

Hutton infuriated catastrophists because he believed that the earth was hundreds of millions of years old

events that must have occurred during the Siccar Point (Hutton)

-the older rocks were deformed through tectonic processes (he didn’t realize this)

- the older rocks were later eroded and then younger units were deposited next

Sir Charles Lyell (1797-1875

He believed that majority of geologists that uniformitarianism was not a joke and his work was in Principles of geology. He believed in a steady-state-Earth, meaning that rocks, processes, and organisms have always existed throughout geological time and that they haven’t changed lots

principles of geology (Lyell)

Lyell Principles of Geology which he built on his own work and the concept of Hutton changed how we understand the earth

William Smith (1769-1839) first geological mapmaker

his main objective was to find coal. by doing this he realized that fossils in rocks tended to follow the Principle of Superposition as well(law of faunal succession). he discovered that groups od fossils are consistent from area to area and are unique through time

correlating fossils from place to place

sedimentary rocks may change from one column to the next but the fossils are the same depending on the time the sediments were deposited

stratigraphic column (created by William Smith)

geologists use stratigraphic columns to help track the different rock formations. rock formations are ordered from oldest to youngest

stratigraphic graph of the Paris Basin

George Cuvir and Alexandre Brongiart used “fossil succession” to show that some units were missing certain parts of the basin. they saw unconformities and noticed that mammal fossils changed with depositional environments

Adam Segwick (1785-1873)

responsible for defining the system that was originally used to define Cambrian rocks

stratigraphic subdivisions

originally defined on the basis of fossil succession through time. when geological studies started fossils were only tools that scientists had to determine relative time. since then we have created radiogenic isotopes to interpret geological time

where does all of this stratigraphic nomenclature come from?

studies the rock layers (strata) and layering (stratification). no matter what frameworks we use geological time units are based on relative time which is defined by fossils, and the position of the rock unit in space.