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<Content><CHAT_MEDIA><SESSION>What%20;are%20;these%20;characteristics%20;?&#10;&gt;&gt;%20;What%20;are%20;pot%45;holes%20;?&#10;&lt;&lt;%20;if%20;the%20;bed%20;of%20;a%20;fast%20;river%20;is%20;uneven%20;pebbles%20;carried%20;in%20;the%20;water%20;swirl%20;and%20;cut%20;circular%20;holes%20;in%20;the%20;river%20;bed.&#10;&gt;&gt;%20;How%20;are%20;waterfalls%20;formed%20;?&#10;&lt;&lt;%20;When%20;a%20;layer%20;of%20;hardrock%20;lies%20;across%20;the%20;course%20;of%20;a%20;river%20;the%20;soft%20;rock%20;on%20;the%20;downstream%20;side%20;is%20;eroded%20;more%20;quickly%20;than%20;the%20;hardrock%20;so%20;it%20;becomes%20;steep%20;after%20;crossing%20;the%20;hardrock,%20;and%20;it%20;becomes%20;a%20;waterfall.%20;</SESSION></CHAT_MEDIA></Content>