About/Contact Index
Way back in February of 2006, I posted three related pages that focused on the geological ages of the Earth, the past configurations of Earth's continents, and the Earth's tectonic plates. Even then it seemed odd to have the separate, but I never got around to merging them until now. The content of the original three pages is still fully intact (if such a thing matters), though altered slightly in presentation. Other changes will eventually be made as well, but for now, the page is finished.
In the never ending pursuit to better understand our planet's history, geologists have taken the time to set up a nifty little system by which they break up the Earth's past in to more manageable lengths of time. Presented for the enlightenment of all is a simplified and abbreviated table of the time scale.
The dates at the right of the table have been rounded to the nearest factor of five, with the exception of the Holocene and the Pleistocene series. Also, the dates given (which are in millions of years) are for the base (beginning) of the associated Series, System, etc. For example, the Holocene (the present) started roughly 0.012 million years ago.
The table does not include the subdivisions of the Series, nor does it include the Quaternary (which roughly incorporates the Holocene and the Pleistocene) or the Tertiary (which covers everything else in the Cenozoic not covered by the Quaternary). The Quaternary and Tertiary have been excluded as there seems to be a disagreement over their use.
| The Geological Ages of the Earth | |||||
|---|---|---|---|---|---|
| MYA = Millions of Years Ago | |||||
| EON | ERA | SYSTEM / SUBSYSTEM |
SERIES | MYA | |
| Phanerozoic | Cenozoic | Neogene | Holocene | 0.012 | |
| Pleistocene | 2 | ||||
| Pliocene | 5 | ||||
| Miocene | 25 | ||||
| Paleogene | Oligocene | 35 | |||
| Eocene | 60 | ||||
| Paleocene | 65 | ||||
| Mesozoic | Cretaceous | Upper | 100 | ||
| Lower | 145 | ||||
| Jurassic | Upper | 160 | |||
| Middle | 175 | ||||
| Lower | 200 | ||||
| Triassic | Upper | 230 | |||
| Middle | 245 | ||||
| Lower | 250 | ||||
| Paleozoic | Permian | Lopingian | 260 | ||
| Guadalupian | 270 | ||||
| Cisuralian | 300 | ||||
| Carboniferous | Pennsylvanian | Upper | 305 | ||
| Middle | 310 | ||||
| Lower | 320 | ||||
| Mississippian | Upper | 325 | |||
| Middle | 345 | ||||
| Lower | 360 | ||||
| Devonian | Upper | 385 | |||
| Middle | 400 | ||||
| Lower | 415 | ||||
| Silurian | Pridoli | 420 | |||
| Ludlow | 425 | ||||
| Wenlock | 430 | ||||
| Llandovery | 445 | ||||
| Ordovician | Upper | 460 | |||
| Middle | 470 | ||||
| Lower | 490 | ||||
| Cambrian | Furongian | 500 | |||
| Series 3 | 515 | ||||
| Series 2 | 520 | ||||
| Lower | 540 | ||||
| Proterozoic | Neoproterozoic | Ediacaran | 630 | ||
| Cryogenian | 850 | ||||
| Tonian | 1000 | ||||
| Mesoproterozoic | Stenian | 1200 | |||
| Ectasian | 1400 | ||||
| Calymmian | 1600 | ||||
| Paleoproterozoic | Statherian | 1800 | |||
| Orosirian | 2050 | ||||
| Rhyacian | 2300 | ||||
| Siderian | 2500 | ||||
| Archean | Neoarchean | 2800 | |||
| Mesoarchean | 3200 | ||||
| Paleoarchean | 3600 | ||||
| Eoarchean | ~4000 | ||||
| Hadean | ~4650 | ||||
The detailed table upon which the above is based can be found here: Overview of Global Boundary Stratotype Sections and Points.
Presented here are a total of 27 maps showing the Earth's continents as they have changed over the course of hundreds of millions of years. These are smaller versions than the original maps by Ron Blakey, which can be found here, along with various other maps and globes covering the same time periods: Mollewide Plate Tectonic Maps of Phanerozoic.
There are also more maps and information here: Paleomap Project.
Welcome to the wonderful world of plate tectonics. Today we're going to cast a light on those unsung heroes of continental creation: tectonic plates. To start, dispel the notion that there are seven tectonic plates (one for each continent, which is also incorrect), for there aren't. The model that I'm using today has no less than 52 tectonic plates, the majority of which are relatively small. There may actually be more plates than this, but I'll stick with 52 for now.
Tectonic plates are divided into two types: Oceanic and Continental. Oceanic plates are made of denser rock than continental plates and are named for the fact that they are under water. Continental plates are made of lighter rock and are the anchors for the continents (in case that wasn't evident). These plates gradually move across the mantle of the Earth, grinding into each other to create mountain ranges or spreading apart allowing for the creation of new crust (a process that generally occurs on the sea floor).
There are seven major plates that dominate the surface of the Earth. Six of these are continental plates while the seventh is an oceanic plate which the Pacific Ocean covers.
There's also a whole slew of smaller plates that account for the remainder of the Earth's surface. The largest of these smaller plates are about half the size of the small major plates. The majority though, are much smaller, some being almost microscopic by comparison.
|
|
|
|
|
Where the tectonic plates meet, various types of boundaries develop, depending on what direction the plates are traveling relative to one another. The three overall boundary types that develope are convergent, divergent and transform. The convergent boundary can be subdivided into subduction zones, obduction zones and orogenic belts.
| TECTONIC PLATE BOUNDARY TYPES | ||
|---|---|---|
| CONVERGENT | Boundaries where plates are moving towards each other. | |
| Subduction Zone | Occurs when an oceanic and a continental plate collide. The denser oceanic plate is forced under the lighter continental plate. | |
| Obduction Zone | Occurs when a continental plate is pushed under an oceanic plate. This is uncommon. | |
| Orogenic Belt | Occurs when continental plates collide and push upwards, forming mountains. | |
| DIVERGENT | Boundaries where plates are moving apart allowing magma to rise up from the mantle, resulting in the creation of new crust. This occurs primarily at undersea ridges, with the most prominent exception being Iceland. | |
| TRANSFORM | Boundaries where plates slide past each other with little or no crust creation or destruction. | |
Now for what all have been waiting for, a visual representation of all these tectonic plates. Below is a map of the previously listed plates. They are categorised using the steradian which is simply the three dimensional equivalent of a radian.
If you're interested or curious about tectonic plates, take a look at Peter Bird's site. His work is what I used to create the above map, as well as where I found the names for the small and obscure plates.
12 January 2010 - Replaced the table of 'Past Continent Images' with one image of fewer colours, and added version 2.1 of the Tectonic Plates map.
7 February 2009 - Added version 2.0 of the Tectonic Plates map. And hello to all the folks from Lewiston Public Schools! For those not in the know, the splendid town of Lewiston is located in, Maine, (just down the road from Derry) and is home of something truly mysterious! What is it?! Who knows! That's what makes it mysterious.
2 October 2008 - Updated some dead links that I discovered yesterday.
January 29, 2006 - Merged "Fun With Plate Tectonics", "The Earth Through Time", and "The Geologic Timescale" and numbered headings.