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Distribution of landmasses of the Paleo-Earth

posted Jul 6, 2011, 8:35 AM by Abel Mendez
Our planet shows different features as it rotates along its axis, sometimes dominated by land and others by ocean. Land areas are distributed predominantly in the Northern Hemisphere (68%) relative to the Southern Hemisphere (32%) as divided by the equator. Coincidentally, the same can be say about the East-West distribution with most in the Eastern Hemisphere (68%) relative to the Western Hemisphere (32%). These hemispheres are divided by an imaginary circle crossing -20° longitude (20°W), which makes the Eastern Hemisphere center at 73° longitude (73°E). As Earth evolved through time these numbers changed dramatically.
    If we focus on East-West areas, two distinctive interpretations can be defined: the side associated with more continental area, the Maximum Facing Area (MFA), and the side associated with more apparent (normal) area, the Maximum Normal Area (MNA). The MFA is sort of East-West hemisphere area division while the MNA is based on the apparent viewable area as a disk. In practice, the longitudinal location of the MFA and MNA are close, but not necessarily the same.
    The MFA is normalized based of the total continental area available in the planet while the MNA is normalized to the total area of the disk (without prior knowledge of the global land area). For example, a MFA of 68% means that 68% of the land area is in one side of the planet, while a MNA of 42% means that up to 42% of the planet's disk area is covered by land at any moment. Therefore, the MNA is somewhat related to the maximum diurnal albedo of the planet as land areas are usually brighter than ocean areas, although clouds tent to minimize the effect.
    Table 1 shows the North-South and East-West analysis of the land areas of Earth's past derived from our Visible Paleo-Earth project datasets. Figure 1 shows the hemisphere of Earth with more apparent area (MNA) in the last 750 million years (the actual longitude value of this side is show in the last column of Table 1). Figure 2 shows the full analysis for current Earth, other periods and further analysis of Table 1 results are available here (some of the previous values were slightly corrected in Table 1). We are using the curves of the Normal Area (i.e. Figure 1, c) to correlate Earth's albedo with land areas, a procedure that will be important to interpret future light curves from Earth-like exoplanets.

Table 1. Distribution of land areas of Earth in the last 750 million years. The global land coverage varied little within 10 to 30%, however, there where large transitions from South to North (Late Triassic, 220 Mya) and from East to West (Early Devonian, 400 Mya). Also, note the extreme clustering of over 95% of the land areas in one side of the planet (MFA) during Pangea (Middle Triassic, 240 Mya) and Rodinia (Precambrian, 750 Mya).

 Age
(Mya)
Age Name
 Land
(%)
 Ocean
(%)
 Land N
(%)
 Land S
(%)
MFA
(%)
 F-lon
(°)
 MNA
(%)
 N-lon
(°)
 000 Present 2971 683268734259
 020 Early Miocene 3070 683268704459
 035 Late Eocene 2971 663469204153
 050 Early Eocene 2872 643672293950
 065 Late Cretaceous (K-Pg) 2674 613977283910
 090 Late Cretaceous23775347833635 -5 
 105 Early Cretaceous2476 54 46 86 40 39 -4 
 120 Early Cretaceous26 74 57 43 90 41 46 
 150 Late Jurassic25 7558 42 92 36 49 
 170 Middle Jurassic26 74 57 43 94 35 52 
 200 Late Triassic27 73 53 47 95 33 59 
 220 Late Triassic28 72 52 48 96 37 62 
 240 Middle Triassic27 73 42 58 98 41 58 
 260 Late Permian26 74 39 61 94 41 59 10 
 280 Early Permian25 75 39 61 93 30 57 
 300 Late Pennsylvanian21 79 34 66 90 35 45 
 340 Middle Mississippian20 80 25 75 86 48 40 
 370 Late Devonian1981 20 80 90 56 30 13 
 400 Early Devonian21 79 13 87 69 74 31 -2 
 430 Middle Silurian19 81 18 82 61 -162 27 160 
 440 Early Silurian19 81 15 85 75 -176 32 170 
 450 Late Ordovician19 81 15 85 71 -175 30 174 
 470 Middle Ordovician19 81 17 83 74 -144 33 176 
 500 Late Cambrian23 77 17 83 79 -139 42 179 
 540 Early Cambrian27 73 20 80 80 -153 53 176 
 560 Late Proterozoic28 72 21 79 78 -162 55 171 
 600 Late Proterozoic30 70 25 75 80 -177 62 161 
 660 Precambrian18 82 18 82 92 176 41 159 
 690 Precambrian13 87 19 81 94 171 33 153 
 750 Precambrian 18 82 38 62 100 156 46 156 


Figure 1. Earth showing the side with more continental area (MNA) in the last 750 million years.

Figure 2. Distribution of land areas of Earth today. The figures are divided in four frames, a context paleomap in an equirectangular projection with annotated percent coverage of ocean and lands areas, including how the land is divided between the northern and southern hemisphere (a), the latitudinal distribution of land areas every 15 degrees (b), the viewable land Facing Area (top curve) and Normal Area (bottom curve) as a function of longitude (c), and the longitudinal distribution of land areas every 30 degrees (d).
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