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四川盆地聚(ju)居(ju)著四川省(sheng)和重慶市大(da)部分人口、居(ju)民主要為(wei)漢族巴蜀民系(xi)。是中國和世界上人口最多的區域之一。
中(zhong)國(guo)著(zhu)名(ming)紅層(ceng)盆地(di)，中(zhong)國(guo)各(ge)大盆地(di)中(zhong)形態最典(dian)型、緯度最南、海(hai)(hai)拔(ba)最低的盆地(di)。位于長江(jiang)上(shang)游地(di)區，海(hai)(hai)拔(ba)500米左右，長江(jiang)把它和東海(hai)(hai)一脈相(xiang)連，它是中(zhong)國(guo)最大的外(wai)流(liu)盆地(di)。
四(si)川盆(pen)(pen)地(di)的面(mian)積(ji)(ji)約26萬余平方(fang)千米（面(mian)積(ji)(ji)是(shi)(shi)居第五(wu)第六位的兩湖盆(pen)(pen)地(di)和銀(yin)額盆(pen)(pen)地(di)的兩倍），占四(si)川省面(mian)積(ji)(ji)的46%。四(si)川盆(pen)(pen)地(di)西(xi)(xi)依(yi)青(qing)藏高原和橫(heng)斷(duan)山(shan)(shan)(shan)(shan)脈(mo)，北(bei)近秦巴山(shan)(shan)(shan)(shan)脈(mo)，與漢中盆(pen)(pen)地(di)相(xiang)望，東(dong)(dong)接湘(xiang)鄂西(xi)(xi)山(shan)(shan)(shan)(shan)地(di)，南連云貴高原，盆(pen)(pen)地(di)北(bei)緣(yuan)米倉(cang)山(shan)(shan)(shan)(shan)，南緣(yuan)大(da)(da)婁山(shan)(shan)(shan)(shan)，東(dong)(dong)緣(yuan)巫山(shan)(shan)(shan)(shan)，西(xi)(xi)緣(yuan)邛崍山(shan)(shan)(shan)(shan)，西(xi)(xi)北(bei)邊(bian)(bian)緣(yuan)龍門(men)山(shan)(shan)(shan)(shan)，東(dong)(dong)北(bei)邊(bian)(bian)緣(yuan)大(da)(da)巴山(shan)(shan)(shan)(shan)，西(xi)(xi)南邊(bian)(bian)緣(yuan)大(da)(da)涼(liang)山(shan)(shan)(shan)(shan)，東(dong)(dong)南邊(bian)(bian)緣(yuan)相(xiang)望于武陵山(shan)(shan)(shan)(shan)。這里的巖石，主要由紫紅色砂巖和頁巖組成。這兩種巖石極易(yi)風(feng)化發育成紫色土(tu)。紫色土(tu)含有(you)豐富(fu)的鈣、磷、鉀等營養元(yuan)素(su)，是(shi)(shi)南方(fang)最肥(fei)沃的自然土(tu)壤。四(si)川盆(pen)(pen)地(di)是(shi)(shi)全國紫色土(tu)分布最集中的地(di)方(fang)，向(xiang)(xiang)有(you)“紫色盆(pen)(pen)地(di)”的美稱。四(si)川盆(pen)(pen)地(di)底(di)部面(mian)積(ji)(ji)約16萬多(duo)平方(fang)千米，按其地(di)理(li)差(cha)異，自西(xi)(xi)向(xiang)(xiang)東(dong)(dong)又可分為成都平原、川中丘陵和川東(dong)(dong)平行(xing)嶺(ling)谷三(san)部分。成都平原西(xi)(xi)方(fang)是(shi)(shi)龍門(men)山(shan)(shan)(shan)(shan)脈(mo)，東(dong)(dong)方(fang)是(shi)(shi)龍泉山(shan)(shan)(shan)(shan)脈(mo)。
四川(chuan)盆(pen)地可明顯分(fen)為邊緣(yuan)山地和盆(pen)地底部兩大(da)部分(fen)，其面積(ji)分(fen)別約為10萬多和16多萬平方公里。邊緣(yuan)山地多中山和低山。
景觀(guan)各要素(su)過渡性明顯，如動植(zhi)物組成上(shang)分別(bie)滲透了華中(zhong)區(qu)、西南區(qu)、青(qing)藏高(gao)原區(qu)和華北區(qu)的成分。邊(bian)緣(yuan)山地(di)區(qu)從(cong)下而上(shang)一般具有2～5個垂直自然分帶。邊(bian)緣(yuan)山地(di)是(shi)四(si)川多(duo)種經濟林木和用材林基(ji)地(di)。農業上(shang)水土流失較為嚴重。盆地(di)底(di)部多(duo)丘陵、低(di)山和平原。地(di)表組成物質(zhi)新而單(dan)一，多(duo)砂泥巖與第四(si)紀沉積物。氣候上(shang)屬中(zhong)亞熱帶，熱量遠比(bi)邊(bian)緣(yuan)山地(di)為高(gao)，但降水量不(bu)及邊(bian)緣(yuan)山地(di)。植(zhi)被(bei)為人工(gong)的次生(sheng)林木所代替，覆被(bei)率低(di)，耕地(di)連片，夏伏(fu)旱和洪澇是(shi)這一地(di)區(qu)最大災害。
盆(pen)(pen)地(di)內部地(di)形地(di)貌(mao)(mao)顯示(shi)出明顯的三分特點，即盆(pen)(pen)西平原地(di)貌(mao)(mao)、盆(pen)(pen)中丘陵地(di)貌(mao)(mao)和盆(pen)(pen)東山地(di)地(di)貌(mao)(mao)，三者(zhe)以龍(long)泉山和華鎣(ying)山為界(jie)。
四川(chuan)盆(pen)地其輪廓形(xing)態(tai)總(zong)體近(jin)似長方(fang)形(xing)，形(xing)似信(xin)封(feng)狀，右(you)傾斜置在(zai)亞洲(zhou)大陸，因(yin)此被地理學者稱之為信(xin)封(feng)盆(pen)地。信(xin)封(feng)盆(pen)地東部(bu)(bu)(bu)頂(ding)點(dian)云陽（靠(kao)近(jin)萬州），南(nan)部(bu)(bu)(bu)頂(ding)點(dian)敘永(靠(kao)近(jin)遵義)，西部(bu)(bu)(bu)頂(ding)點(dian)雅安，北(bei)部(bu)(bu)(bu)頂(ding)點(dian)廣元。信(xin)封(feng)盆(pen)地幾何中(zhong)心(xin)城市(shi)遂寧（幾何中(zhong)心(xin)點(dian)大致在(zai)蓬(peng)溪南(nan)部(bu)(bu)(bu)地區(qu)），中(zhong)北(bei)部(bu)(bu)(bu)（內(nei)頂(ding)角）中(zhong)心(xin)城市(shi)南(nan)充，中(zhong)南(nan)部(bu)(bu)(bu)內(nei)頂(ding)角安岳。
四川盆地西部的成都和東南部的重(zhong)慶皆為國家(jia)中心城市(shi)。
四川盆(pen)(pen)地(di)由盆(pen)(pen)周山地(di)和盆(pen)(pen)地(di)底部構成。
盆周東部為長江三峽，南部為云貴高(gao)原(yuan)，西部為青藏高(gao)原(yuan)，北部為大巴山。
盆地底(di)部主要分為川(chuan)東平(ping)行嶺谷(gu)、川(chuan)中丘陵(ling)(ling)和川(chuan)西(xi)成(cheng)都(dou)平(ping)原三部分。龍泉山(shan)(shan)是成(cheng)都(dou)平(ping)原和川(chuan)中丘陵(ling)(ling)的界山(shan)(shan)，華鎣山(shan)(shan)是川(chuan)中丘陵(ling)(ling)和川(chuan)東平(ping)行嶺谷(gu)的界山(shan)(shan)。
（1）在龍泉山和龍門山、邛(qiong)崍山之(zhi)間的盆西(xi)平(ping)原(yuan)(yuan)，系斷裂下陷由(you)岷江水系的河流(liu)(liu)沖積(ji)而(er)成(cheng)(cheng)(cheng)(cheng)，面(mian)積(ji)約(yue)8000平(ping)方千米(mi)(mi)(mi)(mi)，為我國西(xi)南(nan)最大的平(ping)原(yuan)(yuan)，因成(cheng)(cheng)(cheng)(cheng)都(dou)(dou)位于平(ping)原(yuan)(yuan)之(zhi)中， 故稱成(cheng)(cheng)(cheng)(cheng)都(dou)(dou)平(ping)原(yuan)(yuan)。成(cheng)(cheng)(cheng)(cheng)都(dou)(dou)平(ping)原(yuan)(yuan)海拔460米(mi)(mi)(mi)(mi)～750米(mi)(mi)(mi)(mi)，地(di)(di)勢由(you)西(xi)北向東南(nan)傾(qing)斜，地(di)(di)表平(ping)坦，相對高差一(yi)般(ban)不超過(guo)30米(mi)(mi)(mi)(mi)～50米(mi)(mi)(mi)(mi)，它(ta)由(you)岷江、沱江、涪江、青衣江等八條河流(liu)(liu)沖積(ji)聯綴(zhui)而(er)成(cheng)(cheng)(cheng)(cheng)，土壤(rang)肥(fei)沃，河渠稠(chou)密，有著名的都(dou)(dou)江堰自(zi)流(liu)(liu)灌(guan)溉，自(zi)古(gu)以(yi)來素有“天府”之(zhi)稱。
（2）在龍泉(quan)山和(he)華鎣山之(zhi)間的(de)盆中丘陵(ling)(ling)，地(di)(di)勢低矮，海拔大多在300米(mi)～500米(mi)之(zhi)間，相(xiang)對(dui)高差(cha)50米(mi)～150米(mi)，地(di)(di)勢由北(bei)向(xiang)南(nan)傾(qing)斜，巖(yan)層近于水平，在流水的(de)長期侵蝕切割作用(yong)下，形成臺(tai)階狀的(de)方山丘陵(ling)(ling)，南(nan)部多淺丘，北(bei)部多深丘。丘陵(ling)(ling)地(di)(di)表軟硬相(xiang)間的(de)紫紅色(se)砂(sha)、頁巖(yan)極易風化為紫色(se)土，富(fu)含(han)磷鉀，自然(ran)肥力較(jiao)高，宜種(zhong)性廣，是四川全省糧食(shi)、經濟作物主(zhu)產區。
（3）華鎣(ying)山以東為盆(pen)東平(ping)(ping)行嶺(ling)谷區，由多條近東北西南走向(xiang)的(de)條狀(zhuang)背斜山地(di)(di)與向(xiang)斜寬(kuan)谷組成，山地(di)(di)陡而窄(zhai)，高700米(mi)(mi)(mi)-1000米(mi)(mi)(mi)，其(qi)中，華鎣(ying)山高1705米(mi)(mi)(mi)，為盆(pen)地(di)(di)底部(bu)最高峰(feng)。山地(di)(di)頂(ding)部(bu)的(de)石灰(hui)巖被(bei)雨水(shui)溶(rong)蝕后，常成凹槽(cao)，故(gu)山地(di)(di)大多具有“一山二(er)(er)嶺(ling)一槽(cao)”或(huo)“一山三嶺(ling)二(er)(er)槽(cao)”的(de)特色(se)。山嶺(ling)間(jian)的(de)谷地(di)(di)寬(kuan)而緩，海拔(ba)300米(mi)(mi)(mi)～500米(mi)(mi)(mi)，其(qi)間(jian)丘陵、平(ping)(ping)壩交錯分布，是平(ping)(ping)行嶺(ling)谷區工(gong)農業生產主(zhu)要地(di)(di)區。
四川(chuan)盆(pen)地邊緣山地區屬強烈上升的褶皺(zhou)帶。
地(di)(di)貌(mao)顯著特征是(shi)，海(hai)拔較高，過渡性明顯，均為一(yi)(yi)(yi)(yi)系列中(zhong)(zhong)山(shan)(shan)(shan)(shan)和低山(shan)(shan)(shan)(shan)所圍(wei)繞。盆地(di)(di)北緣(yuan)米(mi)(mi)(mi)(mi)倉山(shan)(shan)(shan)(shan)、大巴(ba)山(shan)(shan)(shan)(shan)近東西走向，是(shi)秦巴(ba)山(shan)(shan)(shan)(shan)地(di)(di)南翼部分，海(hai)拔一(yi)(yi)(yi)(yi)般在1500米(mi)(mi)(mi)(mi)～2200米(mi)(mi)(mi)(mi)之(zhi)間(jian)，山(shan)(shan)(shan)(shan)勢雄偉(wei)，山(shan)(shan)(shan)(shan)坡陡峭，溝(gou)谷深切，相對高差可達(da)500米(mi)(mi)(mi)(mi)～1000米(mi)(mi)(mi)(mi)；南緣(yuan)大婁(lou)山(shan)(shan)(shan)(shan)屬氣勢磅(bang)礴的(de)云貴高原(yuan)之(zhi)一(yi)(yi)(yi)(yi)部分；西緣(yuan)有龍門(men)山(shan)(shan)(shan)(shan)、邛崍山(shan)(shan)(shan)(shan)、峨(e)眉山(shan)(shan)(shan)(shan)，山(shan)(shan)(shan)(shan)脊(ji)海(hai)拔都在1500米(mi)(mi)(mi)(mi)至～3000米(mi)(mi)(mi)(mi)以上(shang)，相對高差可達(da)1000米(mi)(mi)(mi)(mi)，屬中(zhong)(zhong)國(guo)地(di)(di)勢第一(yi)(yi)(yi)(yi)級階梯。峨(e)眉山(shan)(shan)(shan)(shan)頂峰高3099米(mi)(mi)(mi)(mi)，與附近的(de)平原(yuan)相對高差達(da)2660米(mi)(mi)(mi)(mi)，山(shan)(shan)(shan)(shan)勢巍(wei)峨(e)秀(xiu)麗(li)，為中(zhong)(zhong)國(guo)四大佛教名山(shan)(shan)(shan)(shan)之(zhi)一(yi)(yi)(yi)(yi)。
四周為海拔2000～3000米(mi)的(de)(de)山(shan)脈和高原(yuan)所環(huan)繞(rao)，北面(mian)是大(da)巴山(shan)、米(mi)倉山(shan)、龍門山(shan)，西(xi)面(mian)是青(qing)藏高原(yuan)邊緣的(de)(de)邛崍山(shan)、大(da)涼山(shan)，南面(mian)是大(da)婁山(shan)，東面(mian)是巫山(shan)。
無論從(cong)構造還(huan)是(shi)人(ren)(ren)地(di)(di)(di)(di)(di)(di)貌(mao)上(shang)看，四(si)川盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)都(dou)是(shi)一(yi)個典型的(de)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)。它(ta)從(cong)震旦紀(ji)以來就是(shi)地(di)(di)(di)(di)(di)(di)殼(ke)比較穩定(ding)的(de)大型拗陷(xian)(xian)區。晚(wan)三(san)迭(die)紀(ji)的(de)印支(zhi)運(yun)動中成(cheng)為一(yi)個內(nei)陸湖盆(pen)(pen)(pen)，但范圍(wei)要比今日的(de)四(si)川大得多，中生(sheng)(sheng)代(dai)堆積(ji)了厚達3000～4000米(mi)的(de)紫紅(hong)色(se)的(de)砂巖和頁巖，因此人(ren)(ren)們(men)又(you)稱它(ta)為“紅(hong)色(se)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)”或(huo)“紫色(se)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)”。中生(sheng)(sheng)代(dai)末期的(de)四(si)川運(yun)動使(shi)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)周圍(wei)褶皺(zhou)成(cheng)山(shan)，中間(jian)相(xiang)(xiang)對下(xia)陷(xian)(xian)，輪(lun)廓基(ji)本形(xing)(xing)成(cheng)，盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)內(nei)部(bu)地(di)(di)(di)(di)(di)(di)層也發生(sheng)(sheng)大規模的(de)變(bian)形(xing)(xing)。東部(bu)出現一(yi)組北(bei)東向的(de)褶皺(zhou)，稱盆(pen)(pen)(pen)東褶皺(zhou)帶；中部(bu)形(xing)(xing)成(cheng)穹窿構造，稱盆(pen)(pen)(pen)中穹窿帶；西部(bu)表現成(cheng)為盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)沉陷(xian)(xian)帶，為今天盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)的(de)三(san)個地(di)(di)(di)(di)(di)(di)貌(mao)區奠定(ding)了基(ji)礎。新生(sheng)(sheng)代(dai)的(de)喜馬(ma)拉雅(ya)運(yun)動使(shi)周圍(wei)山(shan)地(di)(di)(di)(di)(di)(di)再(zai)次上(shang)升(sheng)，盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)再(zai)次相(xiang)(xiang)對下(xia)陷(xian)(xian)， 成(cheng)都(dou)一(yi)帶下(xia)陷(xian)(xian)更深(shen)。同時，長(chang)江(jiang)切穿巫山(shan)，滾(gun)滾(gun)東流(liu)(liu)，完成(cheng)了統(tong)一(yi)的(de)長(chang)江(jiang)水(shui)系，使(shi)內(nei)流(liu)(liu)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)轉變(bian)為外流(liu)(liu)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)。四(si)川盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)可明顯分(fen)為邊緣山(shan)地(di)(di)(di)(di)(di)(di)和盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)底(di)部(bu)兩大部(bu)分(fen)，其面(mian)積(ji)分(fen)別約為10萬多和16萬多平方(fang)千米(mi)。 四(si)川盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)是(shi)我國最(zui)大的(de)外流(liu)(liu)盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)，面(mian)積(ji)26萬多平方(fang)千米(mi)。四(si)川盆(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)內(nei)部(bu)丘陵、平原交錯(cuo)，地(di)(di)(di)(di)(di)(di)勢(shi)北(bei)高南低(di)。由于地(di)(di)(di)(di)(di)(di)表形(xing)(xing)態的(de)不同，以華(hua)鎣山(shan)、龍泉山(shan)為界。
盆底(di)可分為三部(bu)分：
①華鎣(ying)山(shan)以東為大致平(ping)行的(de)川東嶺谷(gu)，由東北—西南(nan)走向的(de)許多條狀山(shan)體(ti)組成，海拔一般在700～800米，谷(gu)地(di)中多低丘與平(ping)壩，海拔200～500米，是(shi)川東農業和人(ren)口集中的(de)地(di)方。
②華鎣山(shan)(shan)(shan)(shan)和龍泉(quan)山(shan)(shan)(shan)(shan)之間為方(fang)山(shan)(shan)(shan)(shan)丘陵，即川(chuan)中丘陵。區內由于紫紅色砂(sha)頁巖傾(qing)角平緩，受切割后(hou)形成大片方(fang)山(shan)(shan)(shan)(shan)式丘陵。海拔350～450米，相對高(gao)度幾(ji)十米。當(dang)地勞動人(ren)民利用方(fang)山(shan)(shan)(shan)(shan)山(shan)(shan)(shan)(shan)丘土層深(shen)厚的特點，把梯田一(yi)直修到(dao)山(shan)(shan)(shan)(shan)頂(ding)。
③龍泉山(shan)以西為(wei)平原。稱為(wei)川西平原或成都平原，面積6000多平方千米(mi)，是(shi)四(si)川盆(pen)地(di)(di)最大的(de)平原，也是(shi)西南(nan)地(di)(di)區最大的(de)平原，海拔約600米(mi)。
四(si)(si)(si)川盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)屬揚子準地(di)(di)(di)(di)(di)臺四(si)(si)(si)川臺坳(ao)。古(gu)生(sheng)代(dai)時(shi)相(xiang)對隆起，缺乏泥盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)系(xi)和石(shi)炭系(xi)。印支運(yun)動(dong)轉換為(wei)(wei)大(da)(da)型拗陷，晚燕山(shan)(shan)(shan)(shan)運(yun)動(dong)，特別是(shi)喜馬拉雅(ya)運(yun)動(dong)后(hou)發生(sheng)褶皺隆起。盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)的(de)(de)(de)格局(ju)主(zhu)(zhu)要受北(bei)東—南西(xi)向及(ji)北(bei)西(xi)向兩條(tiao)構(gou)造線控制，構(gou)成(cheng)了典(dian)型的(de)(de)(de)菱形(xing)(xing)盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)，四(si)(si)(si)川廣(guang)元(yuan)、四(si)(si)(si)川雅(ya)安(an)、四(si)(si)(si)川敘永為(wei)(wei)菱形(xing)(xing)的(de)(de)(de)四(si)(si)(si)頂(ding)點，東西(xi)兩邊稍長，為(wei)(wei)380～430公里，南北(bei)兩邊略(lve)短，為(wei)(wei)310～330公里。以(yi)上菱形(xing)(xing)四(si)(si)(si)頂(ding)點的(de)(de)(de)連線與盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)內(nei)650～750米(mi)的(de)(de)(de)等高線大(da)(da)體相(xiang)當，盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)底部(bu)(bu)與邊緣(yuan)山(shan)(shan)(shan)(shan)地(di)(di)(di)(di)(di)也以(yi)此(ci)為(wei)(wei)分(fen)(fen)界(jie)。四(si)(si)(si)川盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)在距(ju)今(jin)1.4億(yi)年以(yi)前(qian)，還(huan)是(shi)內(nei)陸湖盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)。至距(ju)今(jin)6.6千萬年時(shi)，盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)邊緣(yuan)山(shan)(shan)(shan)(shan)地(di)(di)(di)(di)(di)迅速隆升，長江中(zhong)(zhong)上游水(shui)系(xi)開始溝(gou)通。盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)內(nei)湖水(shui)東瀉(xie)奠定了現今(jin)之地(di)(di)(di)(di)(di)貌形(xing)(xing)態。盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)邊緣(yuan)多(duo)低山(shan)(shan)(shan)(shan)和中(zhong)(zhong)山(shan)(shan)(shan)(shan)，山(shan)(shan)(shan)(shan)勢(shi)陡峻，發源盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)邊緣(yuan)山(shan)(shan)(shan)(shan)地(di)(di)(di)(di)(di)的(de)(de)(de)河(he)(he)流(liu)(liu)大(da)(da)多(duo)為(wei)(wei)“V”型谷，嶺谷高差都逾500～1 000米(mi)， 地(di)(di)(di)(di)(di)表崎嶇，故歷史上就有“蜀(shu)道難(nan)，難(nan)于上青(qing)(qing)天”之說。山(shan)(shan)(shan)(shan)脊海(hai)拔大(da)(da)多(duo)在2000～3000米(mi)，西(xi)北(bei)部(bu)(bu)與西(xi)部(bu)(bu)可(ke)超過3000～4000米(mi)，如龍(long)門山(shan)(shan)(shan)(shan)4984米(mi)，峨(e)眉(mei)(mei)山(shan)(shan)(shan)(shan)3099米(mi)，小相(xiang)嶺4 791米(mi)。地(di)(di)(di)(di)(di)表廣(guang)泛出露古(gu)生(sheng)代(dai)及(ji)其以(yi)前(qian)的(de)(de)(de)石(shi)灰(hui)巖(yan)(yan)(yan)(yan)(yan)，其次為(wei)(wei)板巖(yan)(yan)(yan)(yan)(yan)、片巖(yan)(yan)(yan)(yan)(yan)、結晶灰(hui)巖(yan)(yan)(yan)(yan)(yan)、石(shi)英巖(yan)(yan)(yan)(yan)(yan)、砂泥巖(yan)(yan)(yan)(yan)(yan)和礫巖(yan)(yan)(yan)(yan)(yan)，局(ju)部(bu)(bu)有花崗巖(yan)(yan)(yan)(yan)(yan)和玄武(wu)巖(yan)(yan)(yan)(yan)(yan)。石(shi)灰(hui)巖(yan)(yan)(yan)(yan)(yan)分(fen)(fen)布(bu)區(qu)可(ke)見(jian)石(shi)林、溶洞、暗河(he)(he)、槽谷等喀斯特地(di)(di)(di)(di)(di)貌，盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)南緣(yuan)興文縣素有“石(shi)林洞鄉”之稱（見(jian)興文石(shi)林）。巫山(shan)(shan)(shan)(shan)十二峰(feng)和金佛山(shan)(shan)(shan)(shan)等名山(shan)(shan)(shan)(shan)主(zhu)(zhu)要也由(you)石(shi)灰(hui)巖(yan)(yan)(yan)(yan)(yan)發育而成(cheng)。由(you)石(shi)灰(hui)巖(yan)(yan)(yan)(yan)(yan)、玄武(wu)巖(yan)(yan)(yan)(yan)(yan)、花崗巖(yan)(yan)(yan)(yan)(yan)等組(zu)成(cheng)的(de)(de)(de)峨(e)眉(mei)(mei)山(shan)(shan)(shan)(shan)及(ji)由(you)砂泥巖(yan)(yan)(yan)(yan)(yan)、礫巖(yan)(yan)(yan)(yan)(yan)組(zu)成(cheng)的(de)(de)(de)青(qing)(qing)城山(shan)(shan)(shan)(shan)，素有“峨(e)眉(mei)(mei)天下秀”、“青(qing)(qing)城天下幽”之稱，為(wei)(wei)中(zhong)(zhong)國(guo)著名游覽勝地(di)(di)(di)(di)(di)。盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)底部(bu)(bu)海(hai)拔多(duo)數在250～700米(mi)，地(di)(di)(di)(di)(di)勢(shi)東南傾，盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)內(nei)各河(he)(he)流(liu)(liu)均由(you)邊緣(yuan)山(shan)(shan)(shan)(shan)地(di)(di)(di)(di)(di)匯聚盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)底部(bu)(bu)的(de)(de)(de)長江干流(liu)(liu)，形(xing)(xing)成(cheng)向心(xin)狀(zhuang)水(shui)系(xi)。地(di)(di)(di)(di)(di)表為(wei)(wei)大(da)(da)面積的(de)(de)(de)中(zhong)(zhong)生(sheng)代(dai)紫紅色砂巖(yan)(yan)(yan)(yan)(yan)與泥巖(yan)(yan)(yan)(yan)(yan)所覆蓋(gai)，故稱為(wei)(wei)“紅層盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)”，是(shi)中(zhong)(zhong)國(guo)中(zhong)(zhong)生(sheng)代(dai)陸相(xiang)紅層分(fen)(fen)布(bu)最集中(zhong)(zhong)地(di)(di)(di)(di)(di)區(qu)。四(si)(si)(si)川盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)為(wei)(wei)丘(qiu)陵(ling)性(xing)盆(pen)(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)，底部(bu)(bu)以(yi)丘(qiu)陵(ling)為(wei)(wei)主(zhu)(zhu)，次為(wei)(wei)低山(shan)(shan)(shan)(shan)和平原。
四(si)(si)川(chuan)盆地(di)屬(shu)揚子陸臺(tai)(tai)一(yi)部(bu)分(fen)，稱為(wei)四(si)(si)川(chuan)陸臺(tai)(tai)，屬(shu)較(jiao)穩定的(de)地(di)區，但仍(reng)經(jing)過兩(liang)次(ci)大規模的(de)海(hai)浸(jin)。第(di)一(yi)次(ci)從(cong)5億多年(nian)前(qian)的(de)寒武(wu)紀開始，延續到3.7億多年(nian)的(de)志留紀，不斷下(xia)陷(xian)成(cheng)了海(hai)洋(yang)盆地(di)，志留紀時(shi)發生(sheng)加(jia)里東運動(dong)，除了西部(bu)的(de)龍門山地(di)槽繼續下(xia)陷(xian)外，其余地(di)區上(shang)升為(wei)陸。2.7億年(nian)前(qian)的(de)石炭紀末，發生(sheng)范圍更大的(de)第(di)二次(ci)海(hai)浸(jin)，盆地(di)再次(ci)為(wei)海(hai)洋(yang)占據。二疊(die)紀時(shi)海(hai)陸交替，形成(cheng)重(zhong)慶附近(jin)的(de)南(nan)酮、松藻、天府等煤礦。二疊(die)紀末，盆地(di)西部(bu)巖(yan)漿(jiang)噴出，峨眉(mei)山小金頂(ding)及清音閣一(yi)帶的(de)玄武(wu)巖(yan)就(jiu)在這時(shi)生(sheng)成(cheng)。
距(ju)今(jin)1.9億年(nian)的(de)(de)三疊紀(ji)(ji)，“印支運(yun)動”使(shi)盆(pen)地邊緣逐(zhu)漸(jian)隆起(qi)成(cheng)山，被(bei)海水淹沒的(de)(de)地區逐(zhu)漸(jian)上升(sheng)成(cheng)陸，由海盆(pen)轉(zhuan)為湖(hu)盆(pen)。當時(shi)(shi)湖(hu)水幾乎占據現(xian)今(jin)四川(chuan)盆(pen)地的(de)(de)全境，稱(cheng)為“蜀湖(hu)”，從(cong)此結束了海浸的(de)(de)歷史。在(zai)中生代漫(man)長的(de)(de)1億多年(nian)里，盆(pen)地氣候溫暖濕潤，到(dao)處生長蕨類、蘇(su)鐵和(he)裸子植物(wu)，是(shi)又(you)一個成(cheng)煤(mei)期，永榮煤(mei)礦即在(zai)三疊紀(ji)(ji)和(he)侏羅紀(ji)(ji)時(shi)(shi)形成(cheng)。東起(qi)長壽、墊(dian)江(jiang)，西(xi)到(dao)江(jiang)油、邛崍，北抵大巴山麓，南到(dao)貴州赤水，還是(shi)天然氣富集區。這一時(shi)(shi)期爬行動物(wu)恐龍(long)稱(cheng)霸(ba)一時(shi)(shi)。1957年(nian)在(zai)合州發(fa)現(xian)的(de)(de)“合州馬門溪龍(long)”身長22米(mi)，高3.5米(mi)，是(shi)中國亞洲(zhou)最大和(he)最完(wan)整的(de)(de)恐龍(long)化(hua)石。
7000萬(wan)年前(qian)的(de)(de)(de)白堊紀(ji)(ji)末期，發生(sheng)又一次強烈的(de)(de)(de)地(di)(di)(di)(di)(di)殼運(yun)動“燕山(shan)運(yun)動”。盆(pen)(pen)地(di)(di)(di)(di)(di)四(si)周山(shan)地(di)(di)(di)(di)(di)繼續隆起(qi)，同(tong)時(shi)產生(sheng)不少(shao)大斷層(ceng)，如西部的(de)(de)(de)龍(long)門山(shan)大斷層(ceng)和(he)東(dong)部的(de)(de)(de)華瑩山(shan)大斷層(ceng)，把盆(pen)(pen)地(di)(di)(di)(di)(di)分為三部分。蜀(shu)(shu)湖(hu)縮小為僅有2萬(wan)平(ping)方公里的(de)(de)(de)蜀(shu)(shu)湖(hu)。封閉(bi)的(de)(de)(de)盆(pen)(pen)地(di)(di)(di)(di)(di)地(di)(di)(di)(di)(di)形(xing)(xing)及急(ji)劇縮小的(de)(de)(de)水面，使(shi)氣(qi)候逐(zhu)漸變得干(gan)熱，沉積物(wu)(wu)(wu)由(you)(you)海相、海陸(lu)交(jiao)替相變為陸(lu)相，大量風化、侵(qin)蝕(shi)、剝(bo)蝕(shi)的(de)(de)(de)物(wu)(wu)(wu)質在盆(pen)(pen)地(di)(di)(di)(di)(di)堆積了數(shu)千米厚，形(xing)(xing)成(cheng)(cheng)紅(hong)色(se)和(he)紫(zi)紅(hong)色(se)的(de)(de)(de)砂、泥、頁巖。裸子植物(wu)(wu)(wu)不斷衰退(tui)，恐(kong)龍(long)滅絕了。內陸(lu)湖(hu)泊在干(gan)燥條件下，經強烈蒸發，濃度增(zeng)大，鹽分不斷積累，形(xing)(xing)成(cheng)(cheng)鹽湖(hu)，后來泥沙掩(yan)埋而保存于(yu)地(di)(di)(di)(di)(di)層(ceng)之中，經過漫長的(de)(de)(de)地(di)(di)(di)(di)(di)質作用形(xing)(xing)成(cheng)(cheng)巖層(ceng)，自貢一帶是著名的(de)(de)(de)井(jing)鹽產地(di)(di)(di)(di)(di)。 2000多(duo)萬(wan)年前(qian)的(de)(de)(de)新(xin)第三紀(ji)(ji)，受(shou)喜馬拉(la)雅(ya)造(zao)山(shan)運(yun)動的(de)(de)(de)影響。距今二、三百萬(wan)年的(de)(de)(de)第四(si)紀(ji)(ji)，地(di)(di)(di)(di)(di)殼再次發生(sheng)構造(zao)運(yun)動。從而，四(si)川(chuan)(chuan)盆(pen)(pen)地(di)(di)(di)(di)(di)由(you)(you)內流(liu)(liu)盆(pen)(pen)地(di)(di)(di)(di)(di)變為外流(liu)(liu)陸(lu)盆(pen)(pen)，由(you)(you)封閉(bi)的(de)(de)(de)內流(liu)(liu)區(qu)變為外流(liu)(liu)區(qu)，由(you)(you)以(yi)(yi)堆積為主(zhu)變為侵(qin)蝕(shi)為主(zhu)，經歷(li)了海盆(pen)(pen)——湖(hu)盆(pen)(pen)——陸(lu)盆(pen)(pen)的(de)(de)(de)滄(cang)桑之變。 第四(si)紀(ji)(ji)是冰川(chuan)(chuan)廣布的(de)(de)(de)時(shi)代，盆(pen)(pen)地(di)(di)(di)(di)(di)西北山(shan)地(di)(di)(di)(di)(di)發育(yu)大量冰川(chuan)(chuan)。冰川(chuan)(chuan)消融后，大量沉積物(wu)(wu)(wu)由(you)(you)岷江、沱江等攜帶，堆積在西部的(de)(de)(de)凹陷區(qu)，即以(yi)(yi)前(qian)的(de)(de)(de)蜀(shu)(shu)湖(hu)之中，最終形(xing)(xing)成(cheng)(cheng)了成(cheng)(cheng)都(dou)平(ping)原。 四(si)川(chuan)(chuan)盆(pen)(pen)地(di)(di)(di)(di)(di)地(di)(di)(di)(di)(di)貌豐富(fu)，平(ping)原7%，丘陵52%，低(di)山(shan)41%。
四(si)川(chuan)盆(pen)地(di)中植(zhi)物近(jin)萬(wan)種，古(gu)老而特(te)有種之多為中國其(qi)他地(di)區所不(bu)及。在(zai)(zai)盆(pen)地(di)邊緣(yuan)山(shan)地(di)及盆(pen)東平行嶺谷(gu)尚可(ke)見水(shui)杉、銀杉、鵝掌楸、檫木(mu)(mu)(mu)、三尖杉、珙桐(tong)、水(shui)青(qing)樹、連(lian)香樹、領春木(mu)(mu)(mu)、金錢槭、蠟梅、杜仲、紅(hong)豆(dou)杉、鐘萼木(mu)(mu)(mu)、福建柏、穗花杉、崖(ya)柏、木(mu)(mu)(mu)瓜紅(hong)等珍稀孑遺(yi)(yi)植(zhi)物與特(te)有種。在(zai)(zai)濕熱河谷(gu)可(ke)見桫欏(luo)、小(xiao)羽(yu)桫欏(luo)、烏毛蕨、華南(nan)紫萁、里(li)白(bai)等古(gu)熱帶(dai)孑遺(yi)(yi)植(zhi)物。 四(si)川(chuan)盆(pen)地(di)的(de)地(di)帶(dai)性植(zhi)被是(shi)亞熱帶(dai)常(chang)綠(lv)闊(kuo)(kuo)葉(xie)(xie)林，其(qi)代表樹種有栲樹、峨眉栲、刺果米櫧、青(qing)岡、曼青(qing)岡、包石櫟、華木(mu)(mu)(mu)荷、大(da)包木(mu)(mu)(mu)荷、四(si)川(chuan)大(da)頭茶、楨楠、潤(run)楠等，海(hai)拔一般情況下(xia)在(zai)(zai)1600～1 800米以下(xia)。其(qi)次有馬尾松、杉木(mu)(mu)(mu)、柏木(mu)(mu)(mu)組成 的(de)亞熱帶(dai)針(zhen)葉(xie)(xie)林及竹(zhu)林。 邊緣(yuan)山(shan)地(di)從(cong)下(xia)而上是(shi)常(chang)綠(lv)闊(kuo)(kuo)葉(xie)(xie)林、常(chang)綠(lv)闊(kuo)(kuo)葉(xie)(xie)與落葉(xie)(xie)闊(kuo)(kuo)葉(xie)(xie)混(hun)交林，寒溫(wen)帶(dai)山(shan)地(di)針(zhen)葉(xie)(xie)林，局部有亞高山(shan)灌叢草甸。
四川盆(pen)(pen)(pen)(pen)地(di)(di)(di)是(shi)中(zhong)國動(dong)物種類(lei)最多、最齊全的地(di)(di)(di)區(qu)之一。據(ju)統計，除魚類(lei)外，盆(pen)(pen)(pen)(pen)地(di)(di)(di)底(di)部(bu)共有(you)(you)動(dong)物417種，盆(pen)(pen)(pen)(pen)地(di)(di)(di)西緣、北(bei)緣和南(nan)緣山(shan)地(di)(di)(di)分別為487種、317種與288種，其(qi)中(zhong)經濟動(dong)物均(jun)占一半以上。盆(pen)(pen)(pen)(pen)地(di)(di)(di)西緣山(shan)地(di)(di)(di)是(shi)中(zhong)國特(te)有(you)(you)而古老動(dong)物保存最好、最集中(zhong)的地(di)(di)(di)區(qu)，屬于一類(lei)保護動(dong)物的有(you)(you)大(da)熊(xiong)(xiong)貓(mao)(mao)、金絲(si)猴(hou)、扭(niu)角羚、灰(hui)金絲(si)猴(hou)、白(bai)(bai)唇(chun)鹿等。還有(you)(you)珍貴特(te)有(you)(you)動(dong)物小熊(xiong)(xiong)貓(mao)(mao)、雪豹、鬣羚、短尾猴(hou)、獼猴(hou)、毛冠鹿、水獺及(ji)鴛鴦、血雉、紅腹角雉、綠尾虹雉、白(bai)(bai)腹錦(jin)雞、紅腹錦(jin)雞等。 盆(pen)(pen)(pen)(pen)地(di)(di)(di)西緣的平武(wu)、青川、北(bei)川、寶興、天全、洪雅(ya)、馬邊等地(di)(di)(di)，均(jun)為中(zhong)國大(da)熊(xiong)(xiong)貓(mao)(mao)的主要分布(bu)區(qu)。已設立唐家(jia)河、王朗、臥龍（見臥龍自然保護區(qu)）、蜂桶寨、喇叭河等7處大(da)熊(xiong)(xiong)貓(mao)(mao)、金絲(si)猴(hou)等自然保護區(qu)。 酉陽、馬邊、平武(wu)等盆(pen)(pen)(pen)(pen)地(di)(di)(di)邊緣山(shan)地(di)(di)(di)溪(xi)溝中(zhong)的大(da)鯢(ni)及(ji)長江、金沙江中(zhong)的中(zhong)華(hua)鱘(xun)、白(bai)(bai)鱘(xun)也為四川所特(te)有(you)(you)，均(jun)屬國家(jia)保護動(dong)物。
四川盆地(di)有煤、鐵、天(tian)然氣、石(shi)油(you)、鹽、芒硝(xiao)、石(shi)膏、磷、硫(liu)、鋁、金、銅、錳(meng)、石(shi)墨、汞等礦產資源，其中天(tian)然氣、芒硝(xiao)為全中國(guo)之冠，并有中國(guo)重要的(de)鍶(si)礦。川東北是世界最大(da)的(de)天(tian)然氣富集區之一(yi)，川中和南充等地(di)鹽巖礦儲量很大(da)。
四(si)川盆(pen)地(di)地(di)形閉塞，由于(yu)北(bei)(bei)部(bu)(bu)秦嶺阻擋(dang)冷空(kong)氣，冬季氣溫(wen)高(gao)于(yu)同緯(wei)(wei)度(du)其他地(di)區。最冷月(yue)北(bei)(bei)部(bu)(bu)均溫(wen)3～5℃，南部(bu)(bu)5~8℃，較(jiao)同緯(wei)(wei)度(du)的(de)(de)(de)上海(hai)、湖北(bei)(bei)、安徽及緯(wei)(wei)度(du)偏南的(de)(de)(de)貴州高(gao)1～4℃。盆(pen)地(di)北(bei)(bei)部(bu)(bu)極端(duan)最低溫(wen)-8～-5℃，南部(bu)(bu)-5℃~-2℃。霜(shuang)雪少見，年無霜(shuang)期長280～350天(tian)，同緯(wei)(wei)度(du)上的(de)(de)(de)武(wu)漢冬天(tian)卻霜(shuang)雪不斷(duan)，盆(pen)地(di)位于(yu)長江河谷中的(de)(de)(de)長寧全年無霜(shuang)。 盆(pen)地(di)各地(di)夏季始于(yu)5月(yue)底，終于(yu)9月(yue)中旬，夏長4個月(yue)，溫(wen)度(du)上東高(gao)西(xi)低。盆(pen)地(di)西(xi)部(bu)(bu)夏天(tian)平均氣溫(wen)約25℃，較(jiao)同緯(wei)(wei)度(du)的(de)(de)(de)上海(hai)、武(wu)漢等(deng)城市偏低3-4度(du)，但濕度(du)較(jiao)大(da)，所以悶熱難忍(ren)。
東(dong)(dong)部(bu)(bu)最熱(re)(re)月(yue)氣(qi)(qi)(qi)溫(wen)(wen)(wen)(wen)(wen)(wen)高(gao)達26～29℃，長江河(he)谷(gu)局地(di)達到30℃。盛夏連晴高(gao)溫(wen)(wen)(wen)(wen)(wen)(wen)天氣(qi)(qi)(qi)又造成盆地(di)東(dong)(dong)南(nan)部(bu)(bu)嚴重的夏伏旱。盆地(di)氣(qi)(qi)(qi)溫(wen)(wen)(wen)(wen)(wen)(wen)東(dong)(dong)南(nan)高(gao)西(xi)北低(di)，盆底高(gao)邊緣低(di)； 各地(di)年(nian)均溫(wen)(wen)(wen)(wen)(wen)(wen)16～18℃。10℃以(yi)上活動積溫(wen)(wen)(wen)(wen)(wen)(wen)4500～6000℃，持(chi)續期8～9個月(yue)，屬中亞熱(re)(re)帶。東(dong)(dong)南(nan)部(bu)(bu)的長江河(he)谷(gu)積溫(wen)(wen)(wen)(wen)(wen)(wen)超過6000℃，相(xiang)當于(yu)中國南(nan)嶺以(yi)南(nan)的南(nan)亞熱(re)(re)帶氣(qi)(qi)(qi)候(hou)。盆地(di)氣(qi)(qi)(qi)溫(wen)(wen)(wen)(wen)(wen)(wen)東(dong)(dong)高(gao)西(xi)低(di)，南(nan)高(gao)北低(di)，盆底高(gao)而邊緣低(di)，等(deng)溫(wen)(wen)(wen)(wen)(wen)(wen)線分布(bu)呈(cheng)現同心圓狀。盆地(di)邊緣山地(di)氣(qi)(qi)(qi)溫(wen)(wen)(wen)(wen)(wen)(wen)具(ju)有(you)垂直分布(bu)特點，如峨眉(mei)山、金佛山海拔升(sheng)高(gao)百米，氣(qi)(qi)(qi)溫(wen)(wen)(wen)(wen)(wen)(wen)遞(di)減0.55℃和0.61℃。峨眉(mei)山頂(ding)年(nian)均溫(wen)(wen)(wen)(wen)(wen)(wen)僅(jin)3℃，10℃以(yi)上活動積溫(wen)(wen)(wen)(wen)(wen)(wen)586℃，氣(qi)(qi)(qi)候(hou)上相(xiang)當于(yu)寒(han)溫(wen)(wen)(wen)(wen)(wen)(wen)帶和亞寒(han)帶。
四(si)川盆地(di)(di)年(nian)降(jiang)(jiang)水(shui)量(liang)(liang)(liang)1000～1300毫米(mi)，盆地(di)(di)邊緣山(shan)(shan)地(di)(di)降(jiang)(jiang)水(shui)十(shi)分充沛，如(ru)樂山(shan)(shan)和雅安間的(de)西緣山(shan)(shan)地(di)(di)年(nian)降(jiang)(jiang)水(shui)量(liang)(liang)(liang)為1 500～1800毫米(mi)，為中國(guo)突出的(de)多雨(yu)區(qu)，有“華西雨(yu)屏(ping)”之稱。但冬干、春旱(han)、夏澇、秋綿(mian)雨(yu)，年(nian)內(nei)分配不均(jun)，70～75%的(de)雨(yu)量(liang)(liang)(liang)集中于6～10月。最(zui)大日降(jiang)(jiang)水(shui)量(liang)(liang)(liang)可達300～500毫米(mi)。“巴山(shan)(shan)夜(ye)雨(yu)”自古聞名，夜(ye)雨(yu)占總(zong)雨(yu)量(liang)(liang)(liang)的(de)60～70%以上。盆地(di)(di)區(qu)霧大濕重，云低陰(yin)天多。峨眉山(shan)(shan)、金(jin)佛山(shan)(shan)是中國(guo)霧日最(zui)多地(di)(di)區(qu)之一，年(nian)相對濕度之高也為中國(guo)之冠。盆地(di)(di)年(nian)日照僅900～1300小(xiao)時(shi)，年(nian)太陽輻(fu)射量(liang)(liang)(liang)為370～420千(qian)焦耳(er)/平方(fang)厘米(mi)，均(jun)為中國(guo)最(zui)低值，故(gu)有“蜀犬吠(fei)日”之說。
