Difference between revisions of "3120: Geologic Periods"

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{{comic
 
{{comic
−
| number    = 1606
+
| number    = 3120
−
| date      = November 20, 2015
+
| date      = July 25, 2025
−
| title    = FDF
+
| title    = Geologic Periods
−
| image    = five_day_forecast.png
+
| image    = geologic_periods_2x.png
−
| titletext = You know what they say--if you don't like the weather here in the Solar System, just wait five billion years.
+
| imagesize = 611x557px
 +
| noexpand  = true
 +
| titletext = Geologists claim it's because the earlier Cenozoic used to be called the Tertiary, but that's just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won't tell us about.
 
}}
 
}}
  
 
==Explanation==
 
==Explanation==
−
{{w|Weather forecasting}} is an extremely difficult task, even if it is only for five days. In numerical models, extremely small errors in initial values double roughly every five days for variables such as temperature and wind velocity. So most {{w|Meteorology#Meteorologists|meteorologists}} provide us with only a five-day forecast.
 
  
−
In this comic [[Randall]] takes this to the extreme by first showing a '''Five-Day Forecast''' and then progressing to five-month, year, million, billion and finally trillion-year forecasts, leading to {{tvtropes|WeirdWeather|weather patterns that we don't regularly see.}}
+
This comic depicts a table representing planet Earth's geological time scale. For each period, [[Randall]] highlights his rather idiosyncratic likes and dislikes among their characteristics, instead of accompanying each geological name with facts pertinent to it, such as the duration of the period represented, the state of the Earth (e.g., glaciated), or the flora and fauna most common.
  
−
Since the first weather symbol is the same in all six rows, we can assume it indicates the weather today and not tomorrow, in a trillion years, etc. It is only in the second panel of each row that time has passed per the row's label. Consequently, the last column gives the predictions for four days, four months, ..., four trillion years from today.
+
{| class="wikitable sortable"
 +
!Period and date ({{abbr|{{w|Million years ago|MYA}}|Millions of years ago}})
 +
!Randall's comments
 +
!Explanation
 +
|-
 +
! rowspan="2" | {{w|Precambrian}} (4500⁠–⁠539)
 +
|{{Yes|Life develops}}
 +
|The {{w|Precambrian}} (italicized in the comic since it's not a {{w|Period (geology)|geologic period}}) is the first 88% of Earth's history, including the time 4.1 to 3.4 billion years ago when life on Earth began.
 +
|-
 +
|{{No|Snowball Earth episodes}}
 +
|According to the {{w|Snowball Earth}} hypothesis, during some time spans in the past Earth became nearly or entirely frozen, with no liquid water on the surface. This is similar to the {{w|Greenhouse and icehouse Earth#Icehouse Earth|Icehouse Earth}}, including now, when the planet fluctuates between glacial and interglacial periods.
 +
|-
 +
! rowspan="2" | {{w|Cambrian}} (539⁠–⁠487)
 +
|{{Yes|Trilobites!}}
 +
|{{w|Trilobite|Trilobites}} are related to present-day insects, crabs, and other arthropods, and appeared during the Cambrian.
 +
|-
 +
|{{No|Evolution could stand to calm down a little}}
 +
|The {{w|Cambrian explosion}} was a sudden radiation of complex life forms when nearly all important animal phyla, or precursors to them, appeared. Randall apparently thinks it all happened a little too fast.
 +
|-
 +
! rowspan="2" | {{w|Ordovician}} (487⁠–⁠443)
 +
|{{Yes|Earth might have had rings}}
 +
|Due to the location of impact of one type of meteorite, they may have been part of a {{w|Rings of Earth|planetary ring system around Earth}}, formed by the destruction of a parent body that entered Earth's Roche limit, before colliding with it.
 +
|-
 +
|{{No|Scary volcanic eruption in North America}}
 +
|The volcanic eruptions that deposited {{w|Deicke and Millbrig bentonite layers|layers of ash}} during the Late Ordovician were incredibly large. The volcanoes involved may have been formed during the mountain-building event in {{w|Taconic orogeny|what is now north-eastern North America}}.
 +
|-
 +
! rowspan="2" | {{w|Silurian}} (443⁠–⁠420)
 +
|{{Yes|First land animals}}
 +
|Green plants first became established on land during the Ordovician period, after having evolved ways to protect themselves from desiccation and ultraviolet light. During the Silurian, land animals (mostly arthropods resembling {{w|Kampecaris|millipedes}}) followed the plants.
 +
|-
 +
|{{No|Earth's newfound mold problem}}
 +
| Mold soon evolved to attack them and decompose their remains. A "{{w|Indoor mold|mold problem}}" often refers to mold growing in damp places in a building, causing unpleasant odors and various {{w|Indoor_mold#Health_effects|negative health effects}}.
 +
|-
 +
! rowspan="2" | {{w|Devonian}} (420⁠–⁠359)
 +
|{{Yes|Big mountains in Boston}}
 +
|A section of the present-day Appalachian Range from the Canadian Maritimes to the Carolinas, including what is now the Boston area of Massachusetts, was created during this period. (At the time, Boston was in the tropics, just south of the equator.)
 +
|-
 +
|{{No|Yeah, sure, what those giant killer fish needed was ''armor''}}
 +
|{{w|Placoderm}} fishes, which were common in the Devonian, had plates of {{w|dermal bone}} in the head and thoracic portions of the body. Not all placoderms were giants, or apex predators. These fishes likely had these bony plates because they helped protect them from predators.
 +
|-
 +
! rowspan="2" | {{w|Carboniferous}} (359⁠–⁠299)
 +
|{{Yes|Cool forests}}
 +
|Forests in the Carboniferous lacked the flowering plants and conifers that are common in present-day forests. Instead, forests were dominated by giant versions of today's {{w|Lycopodiaceae|club mosses}}, {{w|Equisetidae|horsetails}}, and {{w|Marattiaceae|ferns}}, as well as by several plant lineages that are now extinct. {{w|File:Meyers b15 s0272b.jpg|Artists' depictions}} of such forests are exotic-looking and considered "cool" by Randall.
 +
|-
 +
|{{No|Bugs too big}}
 +
|Carboniferous '{{w|Carboniferous#Terrestrial invertebrates|bugs}}' included the largest-ever known land invertebrate, a {{w|Arthropleura|2.6 m millipede-like animal}}; the largest-ever known flying insect, resembling a {{w|Meganeura|dragonfly with a wingspan of 75 cm}}; and a {{w|Pulmonoscorpius|70 cm scorpion}}.
 +
|-
 +
! rowspan="2" | {{w|Permian}} (299⁠–⁠252)
 +
|{{Yes|Pangea}}
 +
|{{w|Pangaea}} was the most recent {{w|supercontinent}} containing nearly all of Earth's landmass.
 +
|-
 +
|{{No|Google "The Great Dying"}}
 +
|{{w|Permian-Triassic extinction event|The Great Dying}} occurred at the end of the Permian and is the most severe of Earth's {{w|Extinction event#The "Big Five" mass extinctions|'Big Five' mass extinction events}}. In it, 80% of marine species and 70% of terrestrial vertebrate species were wiped out.
 +
|-)
 +
! rowspan="2" | {{w|Triassic}} (252⁠–⁠201)
 +
|{{Yes|Tanystropheus}}
 +
|The ''{{w|Tanystropheus}}'' was an {{w|Archosauromorpha|Archosauromorph}} with a proportionally unusually long neck (as depicted in the comic).
 +
|-
 +
|{{No|Damage to Canada still visible from space at Manicouagan}}
 +
|{{w|Manicouagan Reservoir}} is a ring-shaped lake, the remains of the crater caused by a 5 km (3 mi) asteroid hitting {{w|Quebec}}.
 +
|-
 +
! rowspan="2" | {{w|Jurassic}} (201⁠–⁠143)
 +
|{{Yes|Birds}}
 +
|The {{w|Avialae|ancestors of modern birds}} emerged during the Jurassic. A common 'fun fact' about birds is that they are modern-day dinosaurs, as the ancestors of today's birds were some of the few dinosaurs to survive the {{w|Cretaceous–Paleogene extinction event}}. Randall has repeatedly expressed interest in this fact, and has repeatedly mentioned it in his comics.
 +
|-
 +
|{{No|Parasitoid wasps}}
 +
|{{w|Parasitoid wasp}}s reproduce by implanting their eggs into still-living animals, whose bodies are then eaten from the inside out by the wasp's larva. It is such a grisly process that it caused a {{w|Parasitoid wasp#In culture|crisis of faith}} among 19th-century European scholars.
 +
|-
 +
! rowspan="2" | {{w|Cretaceous}} (143⁠–⁠66)
 +
|{{Yes|Raptors}}
 +
| rowspan="2" |{{w|Dromaeosauridae|Raptors}}, especially {{w|Velociraptors}}, are a [[Category:Velociraptors|trope]] within xkcd, especially in its early years. They were popularized by their appearance in the ''[[:Category:Jurassic Park|Jurassic Park]]'' film series. In the films, velociraptors are depicted as small (shorter than adult humans) bipedal scaled dinosaurs which frequently attacked and killed humans. Velociraptors and the irrational fear of being attacked by them in the modern world are a subject of several [[xkcd]] strips. Thus, "raptors" appears in both the "Favorites" and "Complaints" columns of the table.
 +
|-
 +
|{{No|Raptors}}
 +
|-
 +
! rowspan="2" | {{w|Paleogene}} (66⁠–⁠23)
 +
|{{Yes|Pretty horseys!!!}}
 +
|Fossils of members of the {{w|Equidae|horse family}} first appear during this period. Horses, fossil and extant, are prime examples of {{w|charismatic megafauna}} ("Pretty horseys!"). The rapid diversification of horses from a presumed single common ancestor is an oft-cited example of mammalian adaptive radiation.
 +
|-
 +
|{{No|Paleocene-eocene thermal maximum}}
 +
|The {{w|Paleocene–Eocene Thermal Maximum}} was a time when the global average temperature rose by 5-8 °C in a relatively short period of time. It can be viewed as a slower version of [[:Category:Climate change|climate change, which Randall has repeatedly complained about]].
 +
|-
 +
! rowspan="2" | {{w|Neogene}} (23⁠–⁠2.6)
 +
|{{Yes|Forests of ''Dracaena'' dragonblood trees}}
 +
|''{{w|Dracaena draco}}'' and ''{{w|Dracaena cinnabari}}'' trees are a source of {{w|dragon's blood}}, a naturally occurring bright red resin used as a varnish and a dye.
 +
|-
 +
|{{No|Zanclean flood}}
 +
|The {{w|Zanclean flood}} is theorized to be the flood that refilled the Mediterranean Sea. It is possible that Randall included this as a reference to [[1190: Time]], which centers around a flood around the Mediterranean sea similar to the Zanclean flood theory.
 +
|-
 +
! rowspan="2" | {{w|Quaternary}} (2.6⁠–⁠present)
 +
|{{Yes|Burrito invented}}
 +
|Randall jokes that, in the last 2.6 million years, his favorite moment was the invention of the {{w|burrito}}, rather than many other, much more significant discoveries. The precise origin of the burrito is not known, but the {{w|Maya civilization}} made food resembling burritos as early as 1500 BC.
 +
|-
 +
|{{No|Whoever picked the name for the third period of the Cenozoic}}
 +
|The third period of the {{w|Cenozoic Era}} is the Quaternary ("Fourth"), named by Jules Desnoyers in 1829. Randall is riffing on the cognitive disconnect between "third" and "fourth", for which the current geological naming conventions offer no justification.
 +
|}
  
−
When moving past the five-day prediction, the forecast is just a qualified guess based on the time of year. In a month it is Christmas as shown in the second panel of the second row. Then it is January and February so snow is likely, but certainly not something that happens on all days of a winter month.
+
The title text expands on the complaint about the "third" <em>v</em> "fourth" discrepancy in regard to the Quaternary Period by claiming the existence of an unnamed geologic period within the Cenozoic Era "that geologists won't tell us about". As the idea of Earth being billions of years old gained acceptance and we invented tools for dating rocks, "primary" and "secondary" fell away as descriptors for both rock types and rock ages, replaced by terms that convey information about the rocks more accurately. "Tertiary" was applied to "Cenozoic minus Quaternary", and survived in formal nomenclature into the 21st century. No alternative for "Quaternary" has yet been accepted, so the name persists as fodder for cartoonists who wonder, not without cause, how a "third" element in Earth history could be labeled a "fourth" element. The phrase '''x'' that ''y'' won't tell us about' is a common trope in {{w|Conspiracy theory|Conspiracy theories}} in which something is claimed to be hidden from the populace.
  
−
Looking at the five-year forecast, guesses are made as to what the weather will be like at the same time of year. For these first three predictions the weather symbols are all of the same three types: Sun, clouds and some kind of {{w|precipitation}}, rain or snow, with the temperature ranging from 21 to 44&nbsp;°F (-6.1 to 6.6&nbsp;°C) - winter temperatures.
+
==Transcript==
−
 
+
{{incomplete transcript|Don't remove this notice too soon.}}
−
Then we go into the far future, jumping a million years from panel to panel. But still the weather symbols stay the same. In 3 million years, however, aliens (or advanced humans) attack with energy beams from {{w|flying saucers}}. They are gone a million years later. The temperature range remains the same across the panels except that it rises to 52&nbsp;°F (11&nbsp;°C), a possible reference to global warming, in one panel, and while the attack is going on it rises to 275&nbsp;°F (135&nbsp;°C).
 
−
 
 
−
Once we get to the billion-year mark it actually becomes more meaningful to try to predict the "weather", because now we reach the times when the {{w|Sun}} begins to change. Although the Sun will continue to burn hydrogen for about 5 billion years yet (while in its {{w|Sun#Main sequence|main sequence|}}), it will grow in diameter as it begins to exhaust its supply of fuel. The core will contract to increase the temperature, and the outer layer will then compensate by expanding slightly. This is what is indicated in panels two and three, where the color of the Sun changes towards red as the surface becomes cooler as it expands away from the center of the Sun. The temperature will rise on Earth as indicated in the panels (105&nbsp;°F = 40.5&nbsp;°C and 371&nbsp;°F = 188&nbsp;°C). The temperature will get hot enough in about [http://phys.org/news/2015-02-sun-wont-die-billion-years.html a billion years] that the Earth's oceans will boil away.
 
−
 
 
−
Once it {{w|Sun#After core hydrogen exhaustion|no longer has enough hydrogen}}, the Sun will expand into a {{w|red giant}}. This should not happen until around {{w|Sun#Composition|five billion years from now}}, but in the forecast it is indicated to happen in only three. Maybe this is Randall taking liberties to show what happens during this phase, which would not fit into a four-billion-year forecast. Alternatively it just indicates how uncertain these kinds of forecasts are, or a statement that we may not know for certain that it will take five not three billion years.
 
  
−
In any case, the fourth panel shows the temperature at Earth's position inside the red giant Sun. The color of the panel indicates that we are inside the Sun. The temperature is 71,488,106 degrees Fahrenheit (39,715,597 degrees Celsius). The current temperature of the center of the Sun is "only" 27 million degrees Fahrenheit (15 million degrees Celsius), and although that may rise by a factor of ten during {{w|Stellar nucleosynthesis|helium fusion}}, that will only be at the very core and not out in the solar atmosphere reaching out to Earth. Here the temperature would only be of the order of thousands of degrees Fahrenheit, since the Sun's outer temperature decreases as it increases its diameter. So this panel's temperature also makes little sense. It may involve some ambiguities regarding what the forecast means; the edge of the red giant Sun is predicted to be somewhere near the current orbit of Earth, but the position of the Earth could change. The most likely prediction at the moment is for Earth to move outward, but if the planet is engulfed by the Sun, it would spiral inward, and at some point fall apart. So in some sense "here" for the forecast could become a position deep inside the Sun, where core temperatures could reach 100 million Kelvin. The temperatures shown are unreasonably precise; they probably should have only two or at most three significant figures.
+
:[A table with 3 columns, labelled: "Period", "My favorite part" and "My biggest complaint". There are 13 rows below the labels]
  
−
The red giant phase lasts only half a million years, so a billion years after the Sun has been a red giant its outer atmosphere will definitely have disappeared, leaving only a dim, cool {{w|white dwarf}} to cool down. Given Randall's version of this time schedule, then it will have had about a billion years to cool down, but would still likely be the brightest object in the sky as seen from where the Earth once was. It is not shown in the last panel, where we just see other stars of the Galaxy. The temperature is down to that of the {{w|Cosmic microwave background|background radiation}}. Today this radiation has a temperature of 2.72548 kelvin = -270.4245&nbsp;°C = -454.7641&nbsp;°F. That is a few degrees F colder than what is shown in the comic, which states the temperature is -452&nbsp;°F = 4.26 kelvin. This higher temperature may have been chosen to reflect that even the light from other stars would increase the actual temperature.
+
:[Row 1: Period:] ''Precambrian''
 +
:[My favorite part:] Life develops
 +
:[My biggest complaint:] Snowball Earth episodes
  
−
In the last panel with trillions of years, we jump right past the Sun's red giant phase to a panel looking much like the one after five billion years with only other stars. Over the next three trillion years the stars become fewer and fewer and dimmer and dimmer as they run out of fuel and fewer new stars form. After four trillion years the background temperature decreases one degree to -453&nbsp;°F as the universe keeps expanding and the wavelength of the radiation does the same, thus decreasing its temperature.
+
:[Row 2: Period:] Cambrian
 +
:[My favorite part:] Trilobites!
 +
:[My biggest complaint:] Evolution could stand to calm down a little
  
−
The title text is a play on comments referring to fast-changing weather on a more ordinary human timescale, such as Mark Twain's quip, "If you don't like the weather in New England now, just wait a few minutes."
+
:[Row 3: Period:] Ordovician
 +
:[My favorite part:] Earth might have had rings
 +
:[My biggest complaint:] Scary volcanic eruption in North America
  
−
A ten-day forecast was used in [[1245: 10-Day Forecast]]. In [[1379: 4.5 Degrees]], Randall looked at the weather over long periods of time as well. in [[1643: Degrees]] he addressed Celsius vs. Fahrenheit for measuring temperature.
+
:[Row 4: Period:] Silurian
 +
:[My favorite part:] First land animals
 +
:[My biggest complaint:] Earth's newfound mold problem
  
−
===Image using Celsius===
+
:[Row 5: Period:] Devonian
 +
:[My favorite part:] Big mountains in Boston
 +
:[My biggest complaint:] Yeah, sure, what those giant killer fish needed was '''''armor'''''
  
−
There is a different user-made version for the picture, using [[3001|Celsius]] instead of Fahrenheit, [[:File:five_day_forecast_Celsius.png|in this image link]].
+
:[Row 6: Period:] Carboniferous
−
 
+
:[My favorite part:] Cool forests
−
==Transcript==
+
:[My biggest complaint:] Bugs too big
−
:[A grid with six rows of five columns, where each row is labeled to the left. For each of the 30 squares a temperature is given in Fahrenheit at the top left. The rest of the square represents the weather as in a weather forecast (or some other relevant items for the comic), mainly in bright colors. Below are the six labels given above each of their five weather symbols with temperature given below these symbols description.]
 
  
−
:'''Your 5-day forecast'''
+
:[Row 7: Period:] Permian
−
:[A bright yellow sun.]
+
:[My favorite part:] Pangea
−
:38°F
+
:[My biggest complaint:] Google "The Great Dying"
−
:[A grey cloud.]
 
−
:41°F
 
−
:[A grey cloud with six lines of blue raindrops below.]
 
−
:36°F
 
−
:[A grey cloud in front of a yellow sun.]
 
−
:40°F
 
−
:[Same as Today]
 
−
:44°F
 
  
−
:'''Your 5-month forecast'''
+
:[Row 8: Period:] Triassic
−
:[Same as Today]
+
:[My favorite part:] Tanystropheus [accompanying the text in this cell is an image of a ''Tanystropheus'' and its characteristic elongated neck, with Cueball standing next to it for scale]  
−
:38°F
+
:[My biggest complaint:] Damage to Canada still visible from space at Manicouagan
−
:[A green Christmas tree with red presents beneath it.]
 
−
:29°F
 
−
:[A grey cloud with four snowflakes below.]
 
−
:21°F
 
−
:[Same as Next 2 Months]
 
−
:24°F
 
−
:[Same as Tomorrow]
 
−
:35°F
 
  
−
:'''Your 5-year forecast'''
+
:[Row 9: Period:] Jurassic
−
:[Same as Today]
+
:[My favorite part:] Birds
−
:38°F
+
:[My biggest complaint:] Parasitoid wasps
−
:[Same as Tomorrow]
 
−
:25°F
 
−
:[Same as Today]
 
−
:36°F
 
−
:[Same as Next 2 Days]
 
−
:37°F
 
−
:[Same as Today]
 
−
:41°F
 
  
−
:'''Your 5-million-year forecast'''
+
:[Row 10: Period:] Cretaceous
−
:[Same as Today]
+
:[My favorite part:] Raptors
−
:38°F
+
:[My biggest complaint:] Raptors
−
:[Same as Today]
 
−
:52°F
 
−
:[Same as Tomorrow]
 
−
:40°F
 
−
:[Two red flying saucers (with bright domes) are shooting energy beams downwards. One of the beams seems to impact with something at the bottom of the panel, which then explodes. Two plumes of smoke rises up from below, drifting to the right.]
 
−
:275°F
 
−
:[Same as Next 3 Days]
 
−
:40°F
 
  
−
:'''Your 5-billion-year forecast'''
+
:[Row 11: Period:] Paleogene
−
:[Same as Today]
+
:[My favorite part:] Pretty horseys!!!
−
:38°F
+
:[My biggest complaint:] Paleocene-eocene thermal maximum
−
:[A larger orange sun.]
 
−
:105°F
 
−
:[A very large red sun.]
 
−
:371°F
 
−
:[A pale yellow panel with no drawing.]
 
−
:71,488,106°F
 
−
:[A night sky with many bright stars.]
 
−
:-452°F
 
  
−
:'''Your 5-trillion-year forecast'''
+
:[Row 12: Period:] Neogene
−
:[Same as Today]
+
:[My favorite part:] Forests of ''Dracaena'' dragonblood trees
−
:38°F
+
:[My biggest complaint:] Zanclean flood
−
:[Same as Next 4 Billion Years]
 
−
:-452°F
 
−
:[A night sky with many stars.]
 
−
:-452°F
 
−
:[A night sky with fewer not so bright stars.]
 
−
:-452°F
 
−
:[A night sky with few dim stars.]
 
−
:-453°F
 
  
−
{{comic discussion}}
+
:[Row 13: Period:] Quaternary
 +
:[My favorite part:] Burrito invented
 +
:[My biggest complaint:] Whoever picked the name for the third period of the Cenozoic
  
−
[[Category:Comics with inverted brightness]]
+
{{comic discussion}}<noinclude>
−
[[Category:Comics with color]]
+
[[Category:Charts]]
−
[[Category:Science]]
+
[[Category:Geology]]
−
[[Category:Space]]
+
[[Category:Velociraptors]]
−
[[Category:Astronomy]]
+
[[Category:Animals]]
−
[[Category:Weather]]
+
[[Category:Food]]
−
[[Category:Aliens]]
+
[[Category:Comics featuring Cueball]]

Latest revision as of 15:08, 9 December 2025

Geologic Periods
Geologists claim it's because the earlier Cenozoic used to be called the Tertiary, but that's just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won't tell us about.
Title text: Geologists claim it's because the earlier Cenozoic used to be called the Tertiary, but that's just a ruse to hide the secret third geologic period, between the Neogene and the Quaternary, that they won't tell us about.

    Explanation[edit]

    This comic depicts a table representing planet Earth's geological time scale. For each period, Randall highlights his rather idiosyncratic likes and dislikes among their characteristics, instead of accompanying each geological name with facts pertinent to it, such as the duration of the period represented, the state of the Earth (e.g., glaciated), or the flora and fauna most common.

    Period and date (MYA) Randall's comments Explanation
    Precambrian (4500⁠–⁠539) Life develops The Precambrian (italicized in the comic since it's not a geologic period) is the first 88% of Earth's history, including the time 4.1 to 3.4 billion years ago when life on Earth began.
    Snowball Earth episodes According to the Snowball Earth hypothesis, during some time spans in the past Earth became nearly or entirely frozen, with no liquid water on the surface. This is similar to the Icehouse Earth, including now, when the planet fluctuates between glacial and interglacial periods.
    Cambrian (539⁠–⁠487) Trilobites! Trilobites are related to present-day insects, crabs, and other arthropods, and appeared during the Cambrian.
    Evolution could stand to calm down a little The Cambrian explosion was a sudden radiation of complex life forms when nearly all important animal phyla, or precursors to them, appeared. Randall apparently thinks it all happened a little too fast.
    Ordovician (487⁠–⁠443) Earth might have had rings Due to the location of impact of one type of meteorite, they may have been part of a planetary ring system around Earth, formed by the destruction of a parent body that entered Earth's Roche limit, before colliding with it.
    Scary volcanic eruption in North America The volcanic eruptions that deposited layers of ash during the Late Ordovician were incredibly large. The volcanoes involved may have been formed during the mountain-building event in what is now north-eastern North America.
    Silurian (443⁠–⁠420) First land animals Green plants first became established on land during the Ordovician period, after having evolved ways to protect themselves from desiccation and ultraviolet light. During the Silurian, land animals (mostly arthropods resembling millipedes) followed the plants.
    Earth's newfound mold problem Mold soon evolved to attack them and decompose their remains. A "mold problem" often refers to mold growing in damp places in a building, causing unpleasant odors and various negative health effects.
    Devonian (420⁠–⁠359) Big mountains in Boston A section of the present-day Appalachian Range from the Canadian Maritimes to the Carolinas, including what is now the Boston area of Massachusetts, was created during this period. (At the time, Boston was in the tropics, just south of the equator.)
    Yeah, sure, what those giant killer fish needed was armor Placoderm fishes, which were common in the Devonian, had plates of dermal bone in the head and thoracic portions of the body. Not all placoderms were giants, or apex predators. These fishes likely had these bony plates because they helped protect them from predators.
    Carboniferous (359⁠–⁠299) Cool forests Forests in the Carboniferous lacked the flowering plants and conifers that are common in present-day forests. Instead, forests were dominated by giant versions of today's club mosses, horsetails, and ferns, as well as by several plant lineages that are now extinct. Artists' depictions of such forests are exotic-looking and considered "cool" by Randall.
    Bugs too big Carboniferous 'bugs' included the largest-ever known land invertebrate, a 2.6 m millipede-like animal; the largest-ever known flying insect, resembling a dragonfly with a wingspan of 75 cm; and a 70 cm scorpion.
    Permian (299⁠–⁠252) Pangea Pangaea was the most recent supercontinent containing nearly all of Earth's landmass.
    Google "The Great Dying" The Great Dying occurred at the end of the Permian and is the most severe of Earth's 'Big Five' mass extinction events. In it, 80% of marine species and 70% of terrestrial vertebrate species were wiped out.
    Triassic (252⁠–⁠201) Tanystropheus The Tanystropheus was an Archosauromorph with a proportionally unusually long neck (as depicted in the comic).
    Damage to Canada still visible from space at Manicouagan Manicouagan Reservoir is a ring-shaped lake, the remains of the crater caused by a 5 km (3 mi) asteroid hitting Quebec.
    Jurassic (201⁠–⁠143) Birds The ancestors of modern birds emerged during the Jurassic. A common 'fun fact' about birds is that they are modern-day dinosaurs, as the ancestors of today's birds were some of the few dinosaurs to survive the Cretaceous–Paleogene extinction event. Randall has repeatedly expressed interest in this fact, and has repeatedly mentioned it in his comics.
    Parasitoid wasps Parasitoid wasps reproduce by implanting their eggs into still-living animals, whose bodies are then eaten from the inside out by the wasp's larva. It is such a grisly process that it caused a crisis of faith among 19th-century European scholars.
    Cretaceous (143⁠–⁠66) Raptors Raptors, especially Velociraptors, are a within xkcd, especially in its early years. They were popularized by their appearance in the Jurassic Park film series. In the films, velociraptors are depicted as small (shorter than adult humans) bipedal scaled dinosaurs which frequently attacked and killed humans. Velociraptors and the irrational fear of being attacked by them in the modern world are a subject of several xkcd strips. Thus, "raptors" appears in both the "Favorites" and "Complaints" columns of the table.
    Raptors
    Paleogene (66⁠–⁠23) Pretty horseys!!! Fossils of members of the horse family first appear during this period. Horses, fossil and extant, are prime examples of charismatic megafauna ("Pretty horseys!"). The rapid diversification of horses from a presumed single common ancestor is an oft-cited example of mammalian adaptive radiation.
    Paleocene-eocene thermal maximum The Paleocene–Eocene Thermal Maximum was a time when the global average temperature rose by 5-8 °C in a relatively short period of time. It can be viewed as a slower version of climate change, which Randall has repeatedly complained about.
    Neogene (23⁠–⁠2.6) Forests of Dracaena dragonblood trees Dracaena draco and Dracaena cinnabari trees are a source of dragon's blood, a naturally occurring bright red resin used as a varnish and a dye.
    Zanclean flood The Zanclean flood is theorized to be the flood that refilled the Mediterranean Sea. It is possible that Randall included this as a reference to 1190: Time, which centers around a flood around the Mediterranean sea similar to the Zanclean flood theory.
    Quaternary (2.6⁠–⁠present) Burrito invented Randall jokes that, in the last 2.6 million years, his favorite moment was the invention of the burrito, rather than many other, much more significant discoveries. The precise origin of the burrito is not known, but the Maya civilization made food resembling burritos as early as 1500 BC.
    Whoever picked the name for the third period of the Cenozoic The third period of the Cenozoic Era is the Quaternary ("Fourth"), named by Jules Desnoyers in 1829. Randall is riffing on the cognitive disconnect between "third" and "fourth", for which the current geological naming conventions offer no justification.

    The title text expands on the complaint about the "third" v "fourth" discrepancy in regard to the Quaternary Period by claiming the existence of an unnamed geologic period within the Cenozoic Era "that geologists won't tell us about". As the idea of Earth being billions of years old gained acceptance and we invented tools for dating rocks, "primary" and "secondary" fell away as descriptors for both rock types and rock ages, replaced by terms that convey information about the rocks more accurately. "Tertiary" was applied to "Cenozoic minus Quaternary", and survived in formal nomenclature into the 21st century. No alternative for "Quaternary" has yet been accepted, so the name persists as fodder for cartoonists who wonder, not without cause, how a "third" element in Earth history could be labeled a "fourth" element. The phrase 'x that y won't tell us about' is a common trope in Conspiracy theories in which something is claimed to be hidden from the populace.

    Transcript[edit]

    Ambox warning green construction.svg This is one of 30 incomplete transcripts:
    Don't remove this notice too soon. If you can fix this issue, edit the page!
    [A table with 3 columns, labelled: "Period", "My favorite part" and "My biggest complaint". There are 13 rows below the labels]
    [Row 1: Period:] Precambrian
    [My favorite part:] Life develops
    [My biggest complaint:] Snowball Earth episodes
    [Row 2: Period:] Cambrian
    [My favorite part:] Trilobites!
    [My biggest complaint:] Evolution could stand to calm down a little
    [Row 3: Period:] Ordovician
    [My favorite part:] Earth might have had rings
    [My biggest complaint:] Scary volcanic eruption in North America
    [Row 4: Period:] Silurian
    [My favorite part:] First land animals
    [My biggest complaint:] Earth's newfound mold problem
    [Row 5: Period:] Devonian
    [My favorite part:] Big mountains in Boston
    [My biggest complaint:] Yeah, sure, what those giant killer fish needed was armor
    [Row 6: Period:] Carboniferous
    [My favorite part:] Cool forests
    [My biggest complaint:] Bugs too big
    [Row 7: Period:] Permian
    [My favorite part:] Pangea
    [My biggest complaint:] Google "The Great Dying"
    [Row 8: Period:] Triassic
    [My favorite part:] Tanystropheus [accompanying the text in this cell is an image of a Tanystropheus and its characteristic elongated neck, with Cueball standing next to it for scale]
    [My biggest complaint:] Damage to Canada still visible from space at Manicouagan
    [Row 9: Period:] Jurassic
    [My favorite part:] Birds
    [My biggest complaint:] Parasitoid wasps
    [Row 10: Period:] Cretaceous
    [My favorite part:] Raptors
    [My biggest complaint:] Raptors
    [Row 11: Period:] Paleogene
    [My favorite part:] Pretty horseys!!!
    [My biggest complaint:] Paleocene-eocene thermal maximum
    [Row 12: Period:] Neogene
    [My favorite part:] Forests of Dracaena dragonblood trees
    [My biggest complaint:] Zanclean flood
    [Row 13: Period:] Quaternary
    [My favorite part:] Burrito invented
    [My biggest complaint:] Whoever picked the name for the third period of the Cenozoic

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    Discussion

    Discovered this explanation fresh off the griddle. The transcript doesn't even exist yet wow. Also, hi! This is my first time commenting! Did I do it right? Giraffequeries (talk) 22:54, 25 July 2025 (UTC)

    (Yes, looks like you did.)
    A couple of hours on, and nobody's attempted the Transcript yet. If you're still around right now-ish and you've got more time than everyone elses seems to have (including me, sorry), that could be your next thing.
    Check prior Transcripts for the right kind of way (and a few wrongs, but hey?), and imagine the words+'markup' being read through the hypothetical screen-readers. That might not know how to 'audible' a table, may at best shout/stress bold-strong/italics-emphasis, but perhaps not correctly.
    But just getting the words down helps the next soul with a few more minutes at hand. Any normal weekend, I'd be happy to do it right now, but I've got to be up in five hours, and I mildly regret just checking right now to see if I might have missed the latest comic popping up when it was a bit earlier and I was prepping my weekend bags. :) 82.132.236.123 01:49, 26 July 2025 (UTC)
    Darn, forgot to say my intended actual personal comment I was just going to add. i.e.: Looks like Randall hasn't forgotten about Raptors! Anyway, goodnight/early-morning (my time).... 82.132.236.123 01:53, 26 July 2025 (UTC)

    I've done my part. Also, Raptors TPS (talk) 02:20, 26 July 2025 (UTC)

    Did anyone else google "The Great Dying"? How about "Manicouagan"? How about "Picture of a dinosaur eating a burrito" (just to prove Randall wrong)?

    Ask and you shall receive (shitty AI pic made in five seconds): https://imgur.com/a/4lVKoqD 2A02:2455:1960:4000:1972:32FB:7958:52D3 18:30, 26 July 2025 (UTC)

    Who wrote this? Tanystropheus wasn't a dinosaur! 70.115.234.146 03:28, 26 July 2025 (UTC)

    Given that this wiki doesn't really like tables, and this one is formatted rather simply, maybe we should just transfer its content to the transcript and retain only explanations in the main part, as separate paragraphs? The Rooster (talk) 08:41, 26 July 2025 (UTC)

    What are you talking about. This wiki loves tables! And it is used extensively. --Kynde (talk) 09:07, 28 July 2025 (UTC)

    Yeah I'm not sure what to do for transcript, comic 2627 is in similar style but not sure if we necessarily want it like that.--Darth Vader (talk) 09:18, 26 July 2025 (UTC)

    Just a small explanation to the Quarternary/Tertiary naming issue because this has become rather obscure and is seldomly spelled out in newer geology textbooks: When the first geologists came up with a table of geologic epochs it consisted of four parts: "Primary", "Secondary", "Tertiary" and "Quarternary". Only the last two names have survived into our time, because the first two parts became split up into the systems that we still use today rather quickly. This is also the main reason that most stratigraphers want to get rid of the terms Tertiary and Quarternary and why Paleogene/Neogene were invented instead. 2003:DD:472A:5500:35F8:1CD8:D274:E286 14:46, 26 July 2025 (UTC)

    Burrito? Surely not, everyone knows its "soft toilet tissue" 2A00:23C8:252D:A301:B573:A9F2:E80C:711B 10:08, 27 July 2025 (UTC)

    I don't know why he doesn't like the Zanclean flood. It would have been a spectacular sight had anyone been around to see it.2A02:8388:1701:E100:60D1:5BC3:D420:5528 16:44, 27 July 2025 (UTC)

    Should the explanation of the Zanclean flood have some sort of reference to 1190: Time? Morgan Wick (talk) 00:38, 28 July 2025 (UTC)

    That would be obvious and could explain his dislike mentioned above. Lots of animals would have died during this event. --Kynde (talk) 09:07, 28 July 2025 (UTC)

    I have deleted my previous comment, as it was in response to text in the Explanation that no longer exists. These Are Not The Comments You Are Looking For (talk) 03:00, 30 July 2025 (UTC)

    Randall is wrong - parisitoid wasps are very cool. 82.13.184.33 08:14, 28 July 2025 (UTC)

    The Quaternary is obviously so called because it's the period of Quatermass. 82.13.184.33 09:46, 28 July 2025 (UTC)

    If y'all disagree with my docutainment interpretation, feel free to erase it again of course, but the common denominator in Randall's table here really is each period's entertainment value as a focal point. Also, I'd like to add that it's not a bad thing at all for a documentary to be entertaining; quite the opposite. For example, I might never have studied geography if it wasn't for films about interesting foreign places and cool-looking books about volcanoes and dinosaurs and weather, all of which I devoured in my childhood. PaulEberhardt (talk) 20:54, 28 July 2025 (UTC)

    Whatever the inspiration, Randall has been using the table as a comic device for a powerful long time, see the category Charts on this wiki, and i.a. the comics 181: Interblag (20061108) and 394: Kilobyte (20080310). 2605:59C8:160:DB08:8552:7338:3C0A:5AFC 06:34, 29 July 2025 (UTC)

    And thus Velociraptors return after (according to the velociraptor category) 12 years of silence, all hail the great Deinonychus! Xkcdjerry (talk) 12:13, 20 August 2025 (UTC)

    Isn't the Quaternary also called "Anthropocene"? It's a really anthropocentric name, but the definition of the period is "since the advent of man". You can't get more anthropocentric than the Quaternary, or Anthropocene! -- 2a04:cec0:1207:653f:1ce3:a4ff:feb2:a5fe (talk) 16:31, 22 August 2025 (please sign your comments with ~~~~)

    The Quaternary is a geologic period, from 2.58 million years ago to the present. The Anthropocene has been proposed (but never yet officially adopted) as an epoch being from various points 'post-Holocene' (an epoch that started after the start of the greater quaternary period), the change-over being as late as the Trinity nuclear test (as the moment at which technogenic radionuclides started to be added to the environment). We are currently in the quaternary period and the subordinate epoch of your choice. Either still the holocene, or maybe at some point (best left to be argued with far more hindsight, presuming anyone cares to) we entered the anthropocene...
    Or, by the time anyone can be sure, they will be far more sure that every anthropocentric idea of dividing up geologic time is critically wrong and there's a much better alternative method of dividing it all up, with completely different names. ;) 20:44, 22 August 2025 (UTC)
    I'm not sure how widespread this is, but in older Czech literature at least, "Primary" is used to refer to the Paleozoic (Cambrian → Permian), "Secondary" to the Mesozoic (Triassic → Cretaceous), "Tertiary" to Paleogene and Neogene (Paleocene → Pliocene), "Quaternary" to, well, the Quaternary period (Pleistocene → Holocene). 31.30.164.107 21:45, 2 September 2025 (UTC)
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