SearchResearch Challenge (7/7/2019): A couple of questions about Polynesia! (Why so long? What are those clear patches?)

I managed to find wifi! 

As I mentioned last week, I'm touring through French Polynesia for the next two weeks.  It's kind of a long way to go, but it's completely worth it.  Lots of long stretches as we sail from one island to the next.  Many of these are coral atolls, and look a bit like this as we sail by.  They're all low-slung, just barely out of the water.  You wonder how they survive when a big storm comes through.  

Rangiroa seen from the sea.

Or like this, from a satellite image:  

As I've said before, traveling is an endless source of SRS questions. Here, in this place, there are SO many things I've had to look up--my SRS skills are getting a great workout!  What kind of tree is that?  Does the nut from that tree really have fish-stupefying properties?  Really? 

Many of the things I've been seeing need a bit of research to help me understand what I'm seeing.  

This week I've got two Challenges, but on the next cycle, I'll add two more.  But for today, let's start with one slightly difficult Challenge, and a simpler one.  

1.  In researching the dates of initial colonization of Polynesian islands, I noticed a VERY strange incongruity.  Look at the map below.  The blue pins are all island nations that were first colonized around 1000AD.  The red pins (to the left of the long green line) were all colonized around 1000BCE or before.  What happened here between 1000BCE and 1000AD?  Why are the all of the blue pins MUCH later than the red pinned locations?  It's not that far from Samoa to Niue, why didn't anyone colonize that island until 900AD or so?  Generally--why didn't the Polynesians go beyond the green line for a very long time?  

2.  As we're sailing from place to place, it's not uncommon to see large patches of water without any ripples on the surface.  It's something you see nearly everywhere--it's a common effect on lakes, ponds, and oceans.  But what causes these ripple-free regions on the water?   (See below for an image that has a large Y-shaped blank area in the middle. What causes this?)  

As always, be sure to tell us not JUST the answer, but how you figured it out!  What searches worked for you, and if you spend a lot of time on a rathole that doesn't work out, be sure to leave us a comment to that effect.  We can learn a lot from strategies that don't work out.  

Search on!