Several million years ago, a different type of eruption began in the area. These eruptions were smaller and much less explosive. These small eruptions were marked by lava and cinders seeping and sputtering from cones or fissures. The last such small eruption occurred about 80,000 years ago. The remaining volcanic material (less than one percent) in the Yucca Mountain region is a result of these smaller eruptions. Yucca Mountain borders a region known as Crater Flat containing several small cones.