▁a ▁distance ▁of ▁about ▁. ▁ ▁The ▁name ▁of ▁the ▁range ▁dates ▁to ▁Spanish ▁times , ▁when ▁the ▁Sierra ▁La ▁Sal ▁( mean ing ▁the ▁" S alt ▁Mountains ") ▁were ▁a ▁prominent ▁land mark ▁on ▁the ▁Old ▁Spanish ▁Tra il ▁between ▁Santa ▁Fe ▁and ▁Los ▁Angeles . ▁ ▁Ge ology ▁▁▁ ▁The ▁range ▁formed ▁as ▁a ▁result ▁of ▁intr usion ▁of ▁ igne ous ▁rocks ▁and ▁subsequent ▁er os ion ▁of ▁the ▁surrounding ▁less - res istant ▁sed iment ary ▁rocks . ▁The ▁most ▁abund ant ▁ igne ous ▁rocks ▁are ▁por phy rit ic , ▁with ▁phen oc ry st s ▁of ▁horn bl ende ▁and ▁pl agi oc l ase : ▁these ▁rocks ▁are ▁called ▁di or ite ▁in ▁some ▁accounts ▁but ▁tra chy te ▁in ▁at ▁least ▁one ▁other ▁source . ▁Sy en ite , ▁some ▁containing ▁the ▁unusual ▁min eral ▁nose an , ▁makes ▁up ▁a ▁few ▁percent ▁of ▁the ▁ igne ous ▁rocks ▁present . ▁Some ▁of ▁the ▁ igne ous ▁intr us ions ▁have ▁the ▁shapes ▁of ▁la cc ol ith s . ▁A ges ▁of ▁these ▁ igne ous ▁rocks ▁fall ▁in ▁the ▁interval ▁ 2 5 ▁to ▁ 2 8 ▁million ▁years . ▁The ▁mag mas ▁were ▁emp la ced ▁into ▁sed iment ary ▁rocks ▁with ▁ages ▁from ▁Perm ian ▁to ▁C ret ace ous . ▁ ▁The ▁La ▁Sal ▁Mountains ▁r ises ▁high ▁over ▁the ▁surrounding ▁Colorado ▁Pl ate au . ▁ ▁Two ▁other ▁ranges ▁on ▁the ▁Pl ate au , ▁the ▁Ab