Flood basalt or trap basalt is a result of extensive eruption of basaltic lava. The cause of these vast outpourings is thought to be continental rifting combined triggered by a mantle plume/hotspot beneath. As the crust exends decompression of the mantle occurs which causes large volumes of basaltic melt to spill onto the earths surface. Volcanic cones tend not to be formed as the lava is too fluid and flows away from any vents. The Deccan traps,Siberian Traps and Columbia River Basalts are 3 extensive flood basatlt provinces.