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Re: [AAT] primate sea crossings (Re: Flores Man

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  • Marc Verhaegen
    ... ones. Could it geologically be that there initially were islands between Africa & S.America between these capes when these continents split apart? Jose?
    Message 1 of 6 , Nov 1, 2004
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      > >Sometimes there arisoe are mid-Oceanic islands, eg, Iceland & smaller
      ones. Could it geologically be that there initially were islands between
      Africa & S.America between these capes when these continents split apart?
      Jose?

      > The sea-floor spreading takes place at the mid-Atlantic ridge. The rock
      below it rises up and sometimes keeps going as far as sea-level. Iceland has
      this character, hence all its volcanic activity. I suppose other islands
      could have existed in the past, but how would they have disappeared? --Ken

      Erosion perhaps? But then there would have been traces, no? So I guess: no,
      no islands. The "problem" is that NWMs apparently reached S.America
      transatlantically, now >3000 km. Even if this distance (Brazil-W.Africa) was
      only 1400 km or so 40 Ma, it's still a long way? If island-hopping is
      excluded, we still have a pregnant women in estivation in a tree drifting
      from Africa to S.America?

      --Marc
    • Ken Moore
      ... I should have looked at my atlas. The Azores, Ascension and Tristan da Cunha all arise from the mid-Atlantic ridge, and could have been larger 40 Mya.
      Message 2 of 6 , Nov 1, 2004
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        In message <4d3001c4bfee$4c1283e0$0301a8c0@papa> Marc Verhaegen writes:

        >> The sea-floor spreading takes place at the mid-Atlantic ridge. The rock
        >below it rises up and sometimes keeps going as far as sea-level. Iceland has
        >this character, hence all its volcanic activity. I suppose other islands
        >could have existed in the past, but how would they have disappeared? --Ken
        >
        >Erosion perhaps? But then there would have been traces, no? So I guess: no,
        >no islands. The "problem" is that NWMs apparently reached S.America
        >transatlantically, now >3000 km. Even if this distance (Brazil-W.Africa) was
        >only 1400 km or so 40 Ma, it's still a long way? If island-hopping is
        >excluded, we still have a pregnant women in estivation in a tree drifting
        >from Africa to S.America?

        I should have looked at my atlas. The Azores, Ascension and Tristan da
        Cunha all arise from the mid-Atlantic ridge, and could have been larger
        40 Mya. Also interesting is an island whose name is not marked on my
        map, on the equator about 1800 km from Guinea and 1000 km from Brazil.
        Voyagers relying on wind need to choose the season carefully on this
        route. Much of the year it lies in the Doldrums, but possibly the
        north-east trade winds get to it in winter; can any ocean sailors among
        us comment? Then again, wind patterns would be different in an ice age.

        I don't know how much the Atlantic spreading rate varies, but the split
        started c. 160 Mya, so would probably been about 75% of present size by
        the time we are investigating.

        --
        Ken Moore
        ken@...
        Web site: http://www.mooremusic.org.uk/
        I reject emails > 100k automatically: warn me beforehand if you want to send one
      • Richard Parker
        ... smaller ones. ... between Africa & ... Jose? ... The rock ... Iceland ... other ... Like Krakatoa or Thera, maybe? There could be any number of ways for a
        Message 3 of 6 , Nov 1, 2004
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          --- In AAT@yahoogroups.com, Ken Moore <ken@m...> wrote:
          > In message <449901c4bf40$75c2cf50$0301a8c0@papa> Marc Verhaegen
          writes:
          > >Sometimes there arisoe are mid-Oceanic islands, eg, Iceland &
          smaller ones.
          > >Could it geologically be that there initially were islands
          between Africa &
          > >S.America between these capes when these continents split apart?
          Jose?
          >
          > The sea-floor spreading takes place at the mid-Atlantic ridge.
          The rock
          > below it rises up and sometimes keeps going as far as sea-level.
          Iceland
          > has this character, hence all its volcanic activity. I suppose
          other
          > islands could have existed in the past, but how would they have
          > disappeared?
          >
          > --
          > Ken Moore


          Like Krakatoa or Thera, maybe? There could be any number of ways for
          a volcanic island to disappear.

          Richard
        • Marc Verhaegen
          ... rock below it rises up and sometimes keeps going as far as sea-level. Iceland has this character, hence all its volcanic activity. I suppose other islands
          Message 4 of 6 , Nov 2, 2004
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            > >> The sea-floor spreading takes place at the mid-Atlantic ridge. The
            rock below it rises up and sometimes keeps going as far as sea-level.
            Iceland has this character, hence all its volcanic activity. I suppose
            other islands could have existed in the past, but how would they have
            disappeared? --Ken

            > >Erosion perhaps? But then there would have been traces, no? So I guess:
            no, no islands. The "problem" is that NWMs apparently reached S.America
            transatlantically, now >3000 km. Even if this distance (Brazil-W.Africa) was
            only 1400 km or so 40 Ma, it's still a long way? If island-hopping is
            excluded, we still have a pregnant women in estivation in a tree drifting
            from Africa to S.America?

            > I should have looked at my atlas. The Azores, Ascension and Tristan da
            Cunha all arise from the mid-Atlantic ridge, and could have been larger 40
            Mya. Also interesting is an island whose name is not marked on my map, on
            the equator about 1800 km from Guinea and 1000 km from Brazil. Voyagers
            relying on wind need to choose the season carefully on this route. Much of
            the year it lies in the Doldrums, but possibly the north-east trade winds
            get to it in winter; can any ocean sailors among us comment? Then again,
            wind patterns would be different in an ice age. I don't know how much the
            Atlantic spreading rate varies, but the split started c. 160 Mya, so would
            probably been about 75% of present size by the time we are
            nvestigating. -- Ken Moore

            The real cause of seafloor or rift spreadings is still unknown, isn't it?
            It's unknown whether such spreadings are usu. ac- or decelerating?
            There were no ice ages at the time (40 Ma?) I guess.
            What possible explanations do we have for platyrrhines crossing the
            Atlantic?
            - semi-aquaticness (Sera)
            - rafting
            - island-hopping
            -combinations of these
            IIRC, at the time when platyrrhines reached S.America, also caviomorphs did.
            GG Simpson "Splendid isolation" [splendid book IMO --MV] p.140: "these 2
            orders [primates & rodents] have been unusu.successful at island hopping ...
            eventually, members of both hopped to various Caribbean islands"

            --Marc
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