▁the ▁northern ▁half ▁of ▁the ▁Santa ▁Cruz ▁Mountains , ▁formed ▁by ▁the ▁action ▁of ▁plate ▁t ect on ics ▁along ▁the ▁San ▁Andreas ▁F ault . ▁In ▁the ▁middle ▁of ▁the ▁Pen ins ula ▁along ▁the ▁fault ▁is ▁the ▁Cry stal ▁Spr ings ▁Res er voir . ▁Just ▁north ▁of ▁the ▁Cry stal ▁Spr ings ▁res er voir ▁is ▁San ▁Andreas ▁Lake , ▁after ▁which ▁the ▁ge olog ic ▁fault ▁was ▁originally ▁named . ▁ ▁Environment al ▁features ▁The ▁San ▁Francisco ▁Pen ins ula ▁contains ▁a ▁variety ▁of ▁habit ats ▁including ▁est u ar ine , ▁marine , ▁o ak ▁wood land , ▁red wood ▁forest , ▁coast al ▁scr ub ▁and ▁o ak ▁sav anna . ▁There ▁are ▁numerous ▁species ▁of ▁wild life ▁present , ▁especially ▁along ▁the ▁San ▁Francisco ▁Bay ▁est u ar ine ▁sh or eline , ▁San ▁Bruno ▁Mountain , ▁Fitz ger ald ▁Marine ▁Reserve ▁and ▁the ▁for ests ▁on ▁the ▁Mont ara ▁Mountain ▁block . ▁ ▁The ▁county ▁is ▁home ▁to ▁several ▁end anger ed ▁species ▁including ▁the ▁San ▁Francisco ▁g arter ▁s nake , ▁the ▁Mission ▁blue ▁but ter fly ▁and ▁the ▁San ▁Bruno ▁el fin ▁but ter fly , ▁all ▁of ▁which ▁are ▁en demic ▁to ▁San ▁Mate o ▁County . ▁The ▁end anger ed ▁California ▁cla pper ▁rail ▁is ▁also ▁found ▁on ▁the ▁sh ores ▁of ▁San ▁Francisco ▁Bay , ▁in ▁the ▁cities ▁of ▁Bel mont ▁and ▁San ▁Mate o . ▁ ▁A ▁number ▁of ▁not ew orth y ▁par ks ▁and ▁nature ▁pres erves