Before you detach an EBS Volume from an instance, we recommend creating one last snapshot of the volume. As an added safety feature, the Dashboard will not let you delete an EBS Volume until you first detach it from a running instance. When an instance is terminated, any attached volumes will automatically become "detached."
WARNING!
It's important to properly detach an instance before you take a snapshot or delete the volume, otherwise you could possibly corrupt the data on the disk.
There are a couple of different ways you can detach an EBS Volume.
To detach an EBS Volume from an instance, go to the Volumes tab of an instance and click the eraser button and confirm the action.

Under Manage -> Storage -> EBS Volumes, click on the eraser button of a volume.

You can also click the Detach button from the homepage of a selected volume.
