Check out this trick to close all your old Safari tabs in one fell swoop | AustinMacWorks.com

Every time you tap a link to open a Web page in Safari on your iPhone or iPad, it automatically opens a new tab. That’s fine until you realize that you have oodles of old tabs open, making it difficult to find any particular tab. To close all your old tabs in one fell swoop, press and hold on the tab button, then tap Close All X Tabs in the popover that appears.