Bumi tersusun atas beberapa bagian didalamnya, yang meliputi kerak bumi, mantel bumi, dan inti bumi. Tektonik lempeng sendiri membagi bumi tidak hanya berdasarkan komposisinya saja, melainkan berdasarkan sifat elastisitasnya, yaitu litosfer dan astenosfer.
One km-deep scientific drilling within the summit caldera at Izu-Oshima Volcano, which was done for grophysical observation well by ERI in 1996-1998, penetrating the bottom of the volcano (around 40ka), provides me an excellent opportunity to investigate temporal and chemical evolution of basaltic volcano.