Global Warming Causes

Pangaea uLtimathe FuTuRE

Scientists are interested in what the future may be like and how the Earth may eventually look. What will its climate be like? How will its ecosystems function? How many of the changes will be natural, and how many will be human caused? In the case of plate tectonics, geologists have been able to trace the movement of the Earth's plates backward in time in order to determine the geographic positions of the continents and the resulting climates that affected them, such as tropical, polar, or temperate.

The Earth's plate tectonic process continues today, and scientists wonder what the geographic configuration of the continents will one day become. Although these projections are theoretical, they present an intriguing view of what may lie in the future and what role climate may play.

Dr. Christopher R. Scotese, a geologist at the University of Texas, believes that projecting the locations of continents 50 million years from now is not difficult. Projecting beyond that, however, is much more problematic because unpredictable cause-and-effect incidents can drastically change results. "Fifty million years is fairly straightforward. It's like you're driving on the highway and you want to know where you're going to be in 10 minutes. You check the speedometer, do a calculation, and project your present motion. But beyond 50 million years—like on the highway, unexpected things can happen."

Projecting further into the future is more difficult because it involves far more than simple extrapolations. Instead, rules must be developed that govern not only their movements but also where subduction zones and deep ocean trenches will form. They may change shape but seldom disappear altogether because bedrock weighs little compared to the dense ocean crust. Continents literally float, as do mountains. Once formed, they tend to persist and disappear only after ages of erosion wear them down. The difficult part is to predict the development of new subduction zones in the seafloor and to calculate how rapidly such zones will rearrange the continents. "It's hard

(opposite page) Dr. Christopher R. Scotese's Paleomap Project. (A) This is what the Earth's distribution of continents may look like in 50 million years from now. The Atlantic may widen, Africa will collide with Europe closing the Mediterranean, Australia will collide with Southeast Asia, and California will slide northward up the coast to Alaska. (B) This is Pangaea Ultima 250 million years from now. It will form as a result of the subduction of the ocean floor of the North and South Atlantic beneath eastern North America and South America. This supercontinent will have a small ocean basin trapped at its center. (Source: www.scotese.com)

to understand all the forces down there," Scotese says. "There's probably some input from the mantle. It probably has some say on which way the plates go."

O Future world +50 Ma

East Pacific Rise

O Future world +250 Ma

PACIFIC OCEAN

3 Ancient landmass \ Modern landmass

Subduction zone (triangles point in the direction of subduction) — Seafloor spreading ridge

Baja California

PACIFIC

O Future world +50 Ma

Baja California

PACIFIC

OCEAN

East Pacific Rise

O Future world +250 Ma

OCEAN

PACIFIC OCEAN

3 Ancient landmass \ Modern landmass

Subduction zone (triangles point in the direction of subduction) — Seafloor spreading ridge

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Several geologists have predicted that in 50 million years, the tectonic movement of the San Andreas fault will have moved Los Angeles northward to the area of San Francisco. Eventually, Los Angeles will move north as far as Anchorage, Alaska.

In 1998, Dr. Scotese created a project called the Paleomap Project (www.scotese.com), which projects what the continents may look like 50 million years from now and 250 million years from now. He calls the configuration predicted for 250 million years from now Pangaea Ultima. In order to figure out the eventual location of continents, Dr. Scotese used a computer algorithm to simulate the mechanisms that move the plates, such as where subduction zones recycle and melt the plates, where trenches in the ocean floor tear continents apart, where ridges in the ocean floor tear the ocean floor apart and move continents away from one another, and where other continents are being pushed together, creating new mountain ranges.

Dr. Scotese believes the most difficult part of modeling the future distribution of the continents is predicting the development of new subduction zones and determining how aggressive they will be in moving the plates compared to older subduction zones. In addition to the forces on the crust, forces deep inside the Earth's mantle play a part in plate tectonics and are difficult to model.

Dr. Scotese predicts that the processes that will lead to the Earth 250 million years from now, Pangaea Ultima, will begin with the closing of the Mediterranean. Then, 25 to 75 million years from now, Australia will migrate north, collide with Indonesia and Malaysia, then turn counterclockwise and collide with the Philippines and Asia, eventually merging them all together. In addition, Antarctica will migrate northward, upon which its icecap will melt. About 100 million years from now, it will enter the Indian Ocean. Then, 50 million years later, it will settle between Madagascar and Indonesia, making the Indian Ocean an inland sea.

The most drastic change by far will be the closing of the Atlantic Ocean. Then, 200 million years from now, Newfoundland will collide with Africa, and Brazil will butt up against South Africa. Finally, 250 million years from now, all the continents will have merged into a new super continent, Pangaea Ultima, that will encircle the remnants of the old Indian Ocean.

This is just one prediction of what the Earth may look like in the future. Other scientists have projected that instead of the Atlantic Ocean disappearing, the Pacific Ocean may disappear instead, pushing both North and South America into Asia and forming a hypothetical new continent called Amasia.

These are nevertheless hypothetical projections of the Earth's future created by computer models. While no one knows for sure what the Earth will look like in the distant future, it does bring up interesting questions about what the Earth's climate may be like. If the bulk of the continents are located near the equator, what will have happened to those ecosystems that were not tropical? Likewise, what about tropical habitats that now may reside in the mid-latitudes? In addition, if Antarctica migrates north and its ice cap completely melts, what will sea levels be? What will be the composition of seawater, and what will be the new configuration of the major ocean currents?

With a new spatial arrangement of the continents, there will undoubtedly be a new distribution of ocean currents, which in turn will affect global heat distribution. This will affect vegetation distributions, which, in turn, will affect the carbon cycle. Finally, in light of all these hypothetical changes and their effects on energy, heat, and the carbon cycle, what role will global warming have had on all this? Will global warming have been controlled 250 million years earlier so that there are still productive civilizations left to see what the actual Pangaea Ultima will look like? These are the questions climate scientists are working diligently to answer today.

the geological timescale

ERA	period		EPocH	(millions of years)	first life-forms	geology
	Quaternary		Holocene	0.01	Humans	Ice age
			Pleistocene	3
		Neogene	Pliocene	11	Mastodons	cascades
cenozoic			Miocene	26	saber-toothed tigers	Alps
	Tertiary		oligocene	37
		Paleogene	Eocene	54	Whales
			Paleocene	65	Horses, Alligators	Rockies
	cretaceous			135	Birds
Mesozoic	Jurassic			210	Mammals	sierra Nevada Atlantic
	Triassic			250	Dinosaurs
	Permian			280	Reptiles	Appalachians
			Pennsylvanian	310	Trees	ice age
	carboniferous		Mississippian	345	Amphibians Insects	Pangaea
Paleozoic	Devonian			400	sharks
	silurian			435	Land plants	Laursia
	ordovician			500	Fish
	cambrian			544	sea plants shelled animals	Gondwana
Proterozoic				700	Invertebrates
				2500	Metazoans
				3500	Earliest life
Archean				4000		oldest rocks
				4600		Meteorites

IA				Periodic Table of the Elements i-Atomic number																18 VINA
1.00794	IIA				6.941 —		- Symbol								13 14 15 16 17 IIIA IVA VA VIA VIIA					2 He 4.0026
6.941	9.0122						-Atomic weight						11 12 IB IIB		10.81	6c 12.011	14.0067	15.9994	18.9984	20.1798
22.9898	24.3051		3 4 5 6 7 HIB IVB VB VIB VIIB							8 9 10 VIIIB VIIIB VIIIB					26.9815	28.0855	30.9738	32.067	39.948
40.078	44.9559		47.867	50.9415		51.9962	54.938	55.845	58.9332	58.6934	63.546	65.409	69.723	72.61	74,9216	78.96	79.904	85.4678	87.62			88.906		92.9064	95.94	(98)	106.42	112.412	114.818	121.760	127.60	126.9045	131.29
132.9054	137.328	70ir		174.967	178.49	180.948		183.84	186.207	190.23	192.217	195.08	196.9655	200.59	207.2	208.9804	(209)	(210)	(222)
(226)	102 *		(260)	(261)	(262)		(2öü	(263)	(271)	(277)	(284)	(285)	Uus Uuo ? ?
			-^Lanth Actin			Numbers in parentheses are atomic mass numbers of most stable isotopes.
					anoids oids	138.9055		140.115	144.24	150.36	151.966	157.25	158.9253	66 162.^00	164.9303	167.26	168.9342	173.04
						(227)		232.038	231.036	238.028«	(237)	(244)	243	(247)	(247)	(251)	(259)
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(g) none
(c) nonmetallics
element symbol	a.n.
carbon C	6
hydrogen H	1
(g) chalcogen
(c) nonmetallics
element symbol	a.n.
oxygen o	8
polonium Po	84
selenium Se	34
sulfur s	16
tellurium Te	57
ununhexlum Uuh	116
(g) alkali metal
(c) metallics
element symbol	a.n.
cesium cs	55
francium pr	87
lithium y	3
potassium <	19
rubidium Rb	37
sodium Na	11
(g) alkaline earth metal
(c) metallics
element symbol	a.n.
barium Ba	56
beryllium Be	4
calcium Ca	20
magnesium Mg	12
radium Ra	88
strontium Sr	38

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The Chemical Elements

(g) none (c) metallics

element	symbol	a.n.	element	symbol	a.n.
aluminum	Al	13	scandium	Sc	21
bohrium	Bh	107	seaborglum	Sg	106
cadmium	Cd	48	silver	Ag...	47
chromium	Cr	24	tantalum	Ta	73
cobalt	Co	27	technetium	Tc	43
copper	Cu-.	29	thallium	Tl	81
darmstadtium Ds		110	titanium	Ti	22
dubnlum	Db	105	tin	Sn	50
gallium	Ga	31	tungsten	W	74
gold	Au...	79	ununbium	Uub	112
hafnium	Hf	72	ununtrlum	Uut	113
hassium	Hs	108	ununquadium	Uuq	114
Indium	In	49	vanadium	V	23
iridium	lr ****	77	yttrium	Y	39
iron	Fe	26	zinc	Zn	30
lawrencium	Lr	103	zirconium	Zr	40

lead lutetium manganese meitnerium mercury molybdenum nickel niobium osmium palladium platinum rhenium radium roentgenlurm ruthenium rutherfordlum

111 44 104

(g) pnictogen (c) metallics element_symbol a.n.

arsenic antimony bismuth nitrogen phosophorus

ununpentium Uup

33 51 83 7 15 115

(g) none (c) semimetallics element symbol a.n. boron B 5

germanium Ge 32 silicon Si 14

(g) pnictogen (c) metallics element_symbol a.n.

(g) actinoid (c) metallics
element	symbol	a.n.
actinium	Ac	89
americium	Am	95
berkelium	Bk	97
californium	Cf	98
curium	Cm	96
einsteinium	Es	99
fermlum	Fm	100
mendelevium	Md	101
neptunium	Np	93
nobelium	No	102
Plutonium	Pu	94
protactinium	Pa	91
thorium	Th	90
uranium	U	92
(g) halogens (c) nonmetallics
element	symbol	a.n.
astatine	At*	85
bromine	Br	35
chlorine	CI	17
fluorine	F	9
iodine	I	53
ununseptium	Uus*	117

a.n. = atomic number (g) = group (c) = classification

(g) lanthanoid (c) metallics
element	symbol	a.n.
cerium	Ce	58
dysprosium	Dy	66
erbium	Er	68
europium	Eu	63
gadolinium	Gd	64
holmium	Ho	67
lanthanum	La	57
neodymium	Nd	60
praseodymium Pr		59
Promethium	Pm	61
samarium	Sm	62
terbium	Tb	65
thulium	Tm	69
ytterbium	Yb	70
(g) noble gases (c) nonmetallics
element	symbol	a.n.
argon	Ar	18
helium	He	2
krypton	Kr	36
neon	Ne	10
radon	Rn	86
xenon	Xe	54
ununoctium	Uuo	118

* = semimetallics (c) ** = nonmetallics (c) *** = coinage metal (g) **** = precious metal (g)

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