Earth History and Geological Eras Practice Flashcards

Archaean Eon Start Date

$4.0$ billion years ago (BYA)

Archaean Eon End Date

$2.5$ billion years ago (BYA)

Archaean Life Evidence

Origin of life and the presence of microfossils

Archaean Microfossils Age

$3.5$ BYA

Microstromatolites

Microfossils likely representing photosynthetic bacteria

Archaean Rock Formation

Characterized by Earth's earliest igneous and sedimentary rocks

Archean Eon Classification

The earlier of the two formal divisions of Precambrian time

Precambrian Time Range

About $4.6$ BYA to $541$ MYA

Archean Primordial Records

Records of Earth’s primitive atmosphere and oceans emerge

Archean Microbial Domains

Archaea and bacteria

Archean Microbe Evidence Date

$3.5$ - $3.7$ BYA

Ancient Graphite Date

$3.95$ BYA

Ancient Graphite Significance

May have been produced by microbes suggest life emerged before $3.95$ BYA

Archean Atmosphere

Anoxic (lacking oxygen)

Archean Free Oxygen Source

Organic photosynthesis of carbon dioxide and water

Anaerobic Cyanobacteria

Blue-green algae that release oxygen as a by-product

Prokaryotes

Unicellular organisms with rudimentary internal organization

Archean Eon Ending Marker

The appearance of prokaryotes near the end of the eon

Archean Ocean Origin

Condensation of water derived from the outgassing of volcanoes

Archean Marine Iron Source

Submarine volcanoes in oceanic ridges and thick oceanic plateaus

Oxygen Removal Benefit

Removed oxygen was toxic to photosynthetic organisms, allowing anaerobes to develop

Archean Volcanism Result

High concentrations of carbon dioxide in the atmosphere

Archean Atmospheric Greenhouse Effect

Warmed Earth's surface enough to prevent glaciations

Archean Glacial Evidence

No evidence of glaciations found in Archean rocks

Cratons

Stable interior portions of continents

Kenorland

A supercontinent formed by coalesced cratons at the Archean-Proterozoic boundary

Archean-Proterozoic Boundary Date

About $2.5$ BYA

Proterozoic Eon Start Date

$2.5$ BYA

Proterozoic Eon End Date

$539$ million years ago (MYA)

Proterozoic Atmosphere Type

Oxidative atmosphere

Proterozoic Biological Milestones

Eukaryotes and multicellularity

Proterozoic Plate Tectonics

Modern plate tectonics became active

Proterozoic Continental Rifting

Continents colliding and separating into fragments

Proterozoic Metallic Ores

Iron, gold, copper, uranium, and nickel

Ediacara Fauna

The first oxygen-dependent animals identified in Proterozoic rocks

Specific Proterozoic Oxygen Accumulation Interval

$2.3$ - $1.8$ BYA

Banded-Iron Formations (BIFs)

Formations that removed surplus oxygen from the atmosphere globally

Eukaryote Oxygen Threshold

$10\%$ of the present atmospheric level

Megascopic Eukaryotes Appearance

About $2.3$ BYA

Megascopic Eukaryotes Widespread

About $1.8$ BYA

Eukaryote Metabolism

Respiration and oxidative metabolism

Eukaryote Genetic Innovation

Central nucleus splitting into sex cells to pass mixed and variable codes

Proterozoic Continental Shelves

Stable environments developed after $2.5$ BYA facilitating growth of photosynthetic life

Earliest Metazoans Fossils

Sponge-like fossils in rocks dated to $890$ MYA

Metazoans Definition

Animals made up of more than one type of cell

Paleoproterozoic Duration

$2.5$ - $1.6$ BYA

Great Oxygenation Event (GOE) Cause

Photosynthesis by cyanobacteria

Huronian Glaciation

$2.3$ BYA global cooling triggered by the removal of atmospheric methane

Primary Endosymbiosis Date

About $2$ BYA

Paleoproterozoic Global Redox State Change

Shift from anoxic, reducing to oxic, oxidizing environment

Oxygen Toxicity in Paleoproterozoic

Oxygen was a waste product toxic to dominant anaerobic life

Greatest Mass Extinction Cause (Proterozoic)

Release of oxygen molecule as a waste product by cyanobacteria

Banded Iron Formations record

A geological record of ocean iron reacting with released oxygen

Paleoproterozoic Atmospheric Shift

The Great Oxidation Event (GOE)

Atmospheric Methane removal

Oxygen chemically reacted with methane causing a drop in temperature

Snowball Earth severity

The Huronian Glaciation was arguably the longest and most severe event

Eukaryote Origins

Complex cells that form plants, animals, and fungi emerging from Paleoproterozoic crisis

Mesoproterozoic Duration

$1.6$ - $1$ BYA

Mesoproterozoic Nickname

The 'boring billion' stage

Mesoproterozoic Biological Innovation

The evolution of sexual reproduction

Columbia Supercontinent

A supercontinent that broke up during the Mesoproterozoic

Rodinia Supercontinent Formation

Occurred during the Mesoproterozoic era

Secondary Endosymbiosis Groups

Glaucophytes, red algae, and green algae

Communal Living (Proterozoic)

The start of development of multicellular organisms

Neoproterozoic Duration

$1000$ - $539$ MYA

Cryogenian Glaciation Date

$720$ MYA

Cryogenian Phenomenon

Snowball Earth

Ediacaran Fossil Evidence Date

$635$ MYA

Neoproterozoic Animal Lineages Split

Sponges, cnidarians, protostomes, and deuterostomes split $800$ - $600$ MYA

Neoproterozoic Biological Origins

First fungi and charophytes

Ozone Layer Formation cause

Accumulation of $O_2$ from cyanobacterial photosynthesis

Land Colonization factor

Ozone layer blocking UV radiation

Three Neoproterozoic Global Glaciations

Sturtian, Marinoan, and Gaskiers

Continental Weathering Rates result

Consumption of atmospheric $CO_2$ causing a drop in global temperatures

Neoproterozoic Ocean Anoxia

Caused by sea ice blocking ocean-atmosphere connection and photosynthetic drop

Cap Carbonates definition

Carbonate precipitation found directly above glacial rocks

Volcanic CO2 during Ice Ages

Accumulated below ice caps to eventually increase the greenhouse effect and end glaciations

NOE meaning

Neoproterozoic Oxygenation Event

Nutrient released by melting ice

Phosphorus ($P$), fueling photosynthetic life

Silicate Weathering definition

Process that removes $CO_2$ from the atmosphere by reacting with silicate rocks

Phanerozoic Eon Start Date

$539$ MYA

Phanerozoic Divisions

Paleozoic, Mesozoic, and Cenozoic eras

Phanerozoic Biological Trends

Diversification of complex life forms and mass extinctions

Paleozoic Era Start Date

$538.8$ MYA

Paleozoic Era Starting Event

The Cambrian explosion

Paleozoic Era End Date

$252$ MYA

Paleozoic Era Ending Event

The end-Permian extinction

Gondwana supercontinent members

Africa, South America, Australia, Antarctica, and Indian subcontinent

Pangea formation period

End of its assembly occurred during the Paleozoic

Ordovician/Carboniferous Inundation

Greatest floods of continents by shallow seas

Cambrian Period Date Range

$539$ - $487$ MYA

Cambrian Phyla represented

All modern animal phyla

Cambrian Firsts

First vertebrates and first cephalopods

Cambrian Dominant Species

Trilobites

Cambrian Explosion Timing Correction

Started roughly $575$ million years ago with Ediacara fauna

Ordovician Period Date Range

$487$ - $443$ MYA

Ordovician Life Forms

Many invertebrates and armoured fishes

Ordovician Atmosphere CO2 Levels

$14$ - $16$ times higher than today

Ordovician radiation

Intense diversification of marine animal life including most modern phyla

Ordovician Mass Extinction rank

The second largest mass extinction in Earth’s history