Most of its area lies within the so-called Coastal Chain, which extends from Hendaye to Zumaya. The entire coastal section (Punta Turrilla, Cape Higuer), including Jaizkibel (550 m), is composed of sandstone, microconglomerate, and marl terrains (hard section; gypsum beds). On the slopes of Jaizkibel, on the southern side, there is a strip of land formed by limestone and marl (soft section; thin beds); this is followed by another strip, alternating limestone and sandy limestone with marl. The terrains near the Jaizubia channel and at the entrance to the town are alluvial.