臺灣省中央(yang)山(shan)(shan)脈(mo)北(bei)(bei)(bei)(bei)部(bu)最高峰(feng)(feng)(feng)。海(hai)(hai)拔3740米(mi)(mi),僅次于(yu)玉(yu)山(shan)(shan)、雪(xue)(xue)(xue)山(shan)(shan)(副峰(feng)(feng)(feng)除外)及(ji)中央(yang)山(shan)(shan)脈(mo)中段的(de)秀(xiu)姑巒山(shan)(shan)和馬(ma)博拉斯山(shan)(shan),居全省第5位。以南(nan)(nan)(nan)湖(hu)(hu)(hu)大山(shan)(shan)(主(zhu)峰(feng)(feng)(feng))為(wei)核山(shan)(shan),周鄰約(yue)3公里半徑(jing)內,3500米(mi)(mi)以上(shang)高峰(feng)(feng)(feng)共有7座,皆以南(nan)(nan)(nan)湖(hu)(hu)(hu)為(wei)名(ming),簡稱(cheng)北(bei)(bei)(bei)(bei)山(shan)(shan)(3535米(mi)(mi))、北(bei)(bei)(bei)(bei)峰(feng)(feng)(feng)(3580米(mi)(mi))、東(dong)(dong)峰(feng)(feng)(feng)(3639米(mi)(mi))、東(dong)(dong)南(nan)(nan)(nan)峰(feng)(feng)(feng)(3526米(mi)(mi))、中南(nan)(nan)(nan)峰(feng)(feng)(feng)(3500米(mi)(mi))、南(nan)(nan)(nan)山(shan)(shan)(3516米(mi)(mi)),為(wei)西(xi)(xi)注臺灣海(hai)(hai)峽的(de)大甲(jia)溪和東(dong)(dong)入太平(ping)洋的(de)立霧溪分水嶺。山(shan)(shan)匯諸峰(feng)(feng)(feng)皆以粘板巖為(wei)主(zhu)。因高度(du)、位置和地勢適宜,曾是(shi)更(geng)新世冰(bing)川(chuan)(chuan)分布(bu)區(qu),以主(zhu)峰(feng)(feng)(feng)及(ji)其外圍的(de)北(bei)(bei)(bei)(bei)、東(dong)(dong)北(bei)(bei)(bei)(bei)、東(dong)(dong)3峰(feng)(feng)(feng)為(wei)主(zhu),遺(yi)跡保存(cun)甚(shen)多(duo),冰(bing)蝕地形(xing)典型,有冰(bing)斗冰(bing)川(chuan)(chuan)及(ji)山(shan)(shan)谷(gu)冰(bing)川(chuan)(chuan),前者尤(you)多(duo)。中央(yang)凹地(亦(yi)稱(cheng)南(nan)(nan)(nan)湖(hu)(hu)(hu)谷(gu)地)的(de)冰(bing)斗遺(yi)跡保存(cun)最好。南(nan)(nan)(nan)湖(hu)(hu)(hu)大山(shan)(shan)一(yi)帶,冬春(chun)季節(jie)因受來(lai)自太平(ping)洋通(tong)過宜蘭三角(jiao)(jiao)洲平(ping)原上(shang)空深入的(de)東(dong)(dong)北(bei)(bei)(bei)(bei)風,并受大陸(lu)冷氣(qi)(qi)團東(dong)(dong)南(nan)(nan)(nan)移(yi)影響,3000米(mi)(mi)以上(shang)地區(qu)常有短期積雪(xue)(xue)(xue)甚(shen)厚,由此(ci)亦(yi)可(ke)推(tui)知(zhi)本(ben)區(qu)昔時(shi)冰(bing)川(chuan)(chuan)生(sheng)成和冰(bing)蝕地形(xing)發(fa)育(yu)情況。據調查(cha)研(yan)究,在(zai)(zai)南(nan)(nan)(nan)湖(hu)(hu)(hu)主(zhu)峰(feng)(feng)(feng)及(ji)其東(dong)(dong)北(bei)(bei)(bei)(bei)外圍,共已發(fa)現冰(bing)斗地形(xing)不下12處,底(di)高在(zai)(zai)3300米(mi)(mi)以上(shang),尤(you)以3500米(mi)(mi)左(zuo)右(you)為(wei)多(duo)。位于(yu)主(zhu)峰(feng)(feng)(feng)東(dong)(dong)北(bei)(bei)(bei)(bei)坡的(de)一(yi)處,徑(jing)長達(da)2500米(mi)(mi),寬約(yue)1000米(mi)(mi),其西(xi)(xi)壁中部(bu)高約(yue)1000米(mi)(mi)的(de)陡崖(ya),角(jiao)(jiao)度(du)大致60°~70°。在(zai)(zai)此(ci)西(xi)(xi)鄰,更(geng)有長達(da)4000米(mi)(mi),寬約(yue)1500米(mi)(mi)的(de)一(yi)處。估計南(nan)(nan)(nan)湖(hu)(hu)(hu)大山(shan)(shan)冰(bing)斗群形(xing)成時(shi),雪(xue)(xue)(xue)線高度(du)大致相當3400~3500米(mi)(mi)。發(fa)源于(yu)南(nan)(nan)(nan)湖(hu)(hu)(hu)大山(shan)(shan)西(xi)(xi)側的(de)南(nan)(nan)(nan)湖(hu)(hu)(hu)溪及(ji)與其西(xi)(xi)鄰源于(yu)雪(xue)(xue)(xue)山(shan)(shan)東(dong)(dong)北(bei)(bei)(bei)(bei)坡的(de)七家(jia)灣溪等(均(jun)大甲(jia)溪上(shang)源),均(jun)以產一(yi)種可(ke)能為(wei)冰(bing)期殘留的(de)鮭鱒魚類(lei)著(zhu)名(ming),這種陸(lu)封型魚類(lei)即(ji)與冰(bing)川(chuan)(chuan)時(shi)期低溫氣(qi)(qi)候有密切(qie)聯系。