<div style="margin: 12px 0px; font-family: arial; color: #333333; background: #ffffff; border: solid 4px #e5e5e5; width: 100%; clear: left;"><div class="CM_CTB_Content_Wrap" style="margin: 0px; padding: 0px;background-color: #ffffff;"><div style="border-bottom: solid 1px #dcdcdc; white-space: nowrap; margin-bottom: 8px; background-color: #eeeeee ;background-image: url(http://clipmarks.com/images/source-bg.gif); background-repeat: repeat-x; height: 24px; line-height: 24px; vertical-align: middle; padding-bottom: 4px; color: #666666; font-size: 10px;" ><a href="http://clipmarks.com/clip-to-blog/" title="see clips that are hot right now"><img src="http://content.clipmarks.com/blog_embed/2c043b18-76dd-4a47-abf7-dafcdf9a6d3e/382F5B14-8AF1-4CF5-9A4E-63CD20456C85/" alt="" width="19" height="19" border="0" style="vertical-align: middle; margin: 0px 4px; display: inline; border: none; float:none;" /></a>clipped from <a title="http://www.sciencefriday.com/news/051407/news0514071.html" href="http://www.sciencefriday.com/news/051407/news0514071.html" style="font-size: 11px;">www.sciencefriday.com</a></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html">About 1000 miles north of the Great Lakes, near Hudson Bay, Canada, the pull of gravity is a little weaker.</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html">Differences in gravity are not unusual on Earth: “If the Earth was a perfect sphere, the gravitational field would be the same everywhere,”</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html"><div align="center"><img src="http://content8.clipmarks.com/blog_cache/www.sciencefriday.com/img/8F76D920-1374-4451-B050-43835BFCFAD9" alt="grav map" /></div></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html">But our planet’s bumpy surface, the water flow on the planet, and the movement of plates below Earth's crust can all change the pull of gravity.</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html">25 – 45 percent of the Hudson Bay gravitational signal was due to the last Ice Age—20,000 years ago, when a 2-mile-thick Laurentide ice sheet covered Canada, the land sank under the ice. “Although that ice sheet has long disappeared that ice sheet is still recovering,” Tamisiea says. The depression means less mass, which means less pull.</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html">The primary driver of the lower gravity? The data suggests that plate tectonics and mantle convention is responsible.</blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.sciencefriday.com/news/051407/news0514071.html">Tamisiea says that convection probably dragged the crust down, which decreased the mass under Hudson Bay, decreasing the gravitational pull.</blockquote></div><div style="margin: 0px 6px 6px 4px;"><table style="font-size: 11px;border-spacing: 0px;padding: 0px;" cellpadding="0" cellspacing="0" width="100%"><tr><td style="background:transparent;border-width:0px;padding:0px;">&nbsp;</td><td align="right" style="background:transparent;border-width:0px;padding:0px;width:107px" width="107"><a href="http://clipmarks.com/share/382F5B14-8AF1-4CF5-9A4E-63CD20456C85/blog/" title="blog or email this clip"><img src="http://content9.clipmarks.com/images/c2b-foot.png" border="0" alt="blog it" width="107" height="17" style="border-width:0px;padding:0px;margin:0px;" /></a></td></tr></table></div></div>

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