The Grímsneshraun lava-fields in the area cover a total of . The largest of these plains is the Seyðishólar-Kerhólahraun field which covers . Other sizeable plains include the Tjarnarhólahraun field at , the Kálfshólahraun field at and the Álftarhólshraun . The total volume of lava produced in the lava flows of Grímsnes has been estimated at