This study attempts to discuss the possible causes of the crustal low resistive zone based on the magnetotelluric observations in the Western Foothills, Taiwan, The depth and resistivity of this low resistive zone (LRZ) have the values, on the average, of 9 km and 30 ohm-meters, According to the independently geological data, the possible causes of the LRZ are related to the high CO2 activity in Taiwan and the dehydration reactions. The existence of a significant amount of HCO3- in crustal fluid would produce a consequent impact on resistivity.
