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四川(chuan)(chuan)盆地(di)聚居著四川(chuan)(chuan)省和(he)重慶市大部分人口(kou)、居民(min)主要為漢族巴蜀民(min)系。是(shi)中國和(he)世界上人口(kou)最多的區(qu)域之一。
中國著名紅層(ceng)盆地(di)(di)，中國各大(da)盆地(di)(di)中形(xing)態最(zui)典型(xing)、緯度最(zui)南、海(hai)(hai)拔(ba)最(zui)低的盆地(di)(di)。位于長(chang)(chang)江(jiang)上(shang)游地(di)(di)區，海(hai)(hai)拔(ba)500米左右，長(chang)(chang)江(jiang)把(ba)它和東海(hai)(hai)一脈相連，它是(shi)中國最(zui)大(da)的外(wai)流盆地(di)(di)。
四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)的(de)(de)(de)(de)面(mian)(mian)(mian)積(ji)約26萬余平(ping)方千米(mi)（面(mian)(mian)(mian)積(ji)是居第五(wu)第六(liu)位的(de)(de)(de)(de)兩湖盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)和(he)銀(yin)額盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)的(de)(de)(de)(de)兩倍），占四(si)(si)川(chuan)省面(mian)(mian)(mian)積(ji)的(de)(de)(de)(de)46%。四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)西依青(qing)藏高(gao)原和(he)橫(heng)斷山(shan)脈，北(bei)近(jin)秦巴山(shan)脈，與(yu)漢中(zhong)盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)相望(wang)，東(dong)接湘鄂(e)西山(shan)地(di)(di)(di)(di)，南(nan)連云貴高(gao)原，盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)北(bei)緣米(mi)倉山(shan)，南(nan)緣大(da)婁(lou)山(shan)，東(dong)緣巫山(shan)，西緣邛崍山(shan)，西北(bei)邊緣龍門山(shan)，東(dong)北(bei)邊緣大(da)巴山(shan)，西南(nan)邊緣大(da)涼山(shan)，東(dong)南(nan)邊緣相望(wang)于武陵山(shan)。這里(li)的(de)(de)(de)(de)巖(yan)石(shi)，主要由紫(zi)(zi)紅色(se)(se)砂巖(yan)和(he)頁巖(yan)組成(cheng)(cheng)。這兩種巖(yan)石(shi)極易(yi)風(feng)化發(fa)育成(cheng)(cheng)紫(zi)(zi)色(se)(se)土。紫(zi)(zi)色(se)(se)土含有豐富的(de)(de)(de)(de)鈣、磷、鉀等營養元(yuan)素，是南(nan)方最肥沃的(de)(de)(de)(de)自(zi)然土壤。四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)是全(quan)國紫(zi)(zi)色(se)(se)土分(fen)(fen)(fen)布最集中(zhong)的(de)(de)(de)(de)地(di)(di)(di)(di)方，向有“紫(zi)(zi)色(se)(se)盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)”的(de)(de)(de)(de)美稱。四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)底(di)部(bu)面(mian)(mian)(mian)積(ji)約16萬多平(ping)方千米(mi)，按其地(di)(di)(di)(di)理差異，自(zi)西向東(dong)又可(ke)分(fen)(fen)(fen)為成(cheng)(cheng)都(dou)平(ping)原、川(chuan)中(zhong)丘陵和(he)川(chuan)東(dong)平(ping)行嶺谷三(san)部(bu)分(fen)(fen)(fen)。成(cheng)(cheng)都(dou)平(ping)原西方是龍門山(shan)脈，東(dong)方是龍泉(quan)山(shan)脈。
四川盆地(di)可明顯分(fen)(fen)為邊緣山(shan)地(di)和(he)盆地(di)底部兩大部分(fen)(fen)，其面(mian)積分(fen)(fen)別約為10萬多和(he)16多萬平方公里。邊緣山(shan)地(di)多中(zhong)山(shan)和(he)低山(shan)。
景觀各要素過渡(du)性明顯，如動(dong)植(zhi)物組成(cheng)(cheng)(cheng)上(shang)(shang)分別滲透(tou)了(le)華中(zhong)區、西南(nan)區、青(qing)藏高原區和華北區的(de)成(cheng)(cheng)(cheng)分。邊(bian)緣(yuan)(yuan)山(shan)地區從下(xia)而上(shang)(shang)一(yi)般(ban)具(ju)有2～5個(ge)垂(chui)直自然分帶。邊(bian)緣(yuan)(yuan)山(shan)地是四川多種(zhong)經濟林(lin)(lin)木和用材林(lin)(lin)基(ji)地。農(nong)業上(shang)(shang)水土流失較為(wei)嚴重。盆地底部多丘陵(ling)、低(di)山(shan)和平原。地表組成(cheng)(cheng)(cheng)物質新而單一(yi)，多砂泥(ni)巖與第四紀沉(chen)積物。氣候上(shang)(shang)屬中(zhong)亞熱(re)(re)帶，熱(re)(re)量遠比邊(bian)緣(yuan)(yuan)山(shan)地為(wei)高，但降水量不及邊(bian)緣(yuan)(yuan)山(shan)地。植(zhi)被為(wei)人工的(de)次(ci)生林(lin)(lin)木所(suo)代替，覆(fu)被率(lv)低(di)，耕地連片，夏伏旱和洪澇是這一(yi)地區最大災害。
盆地(di)(di)內部(bu)地(di)(di)形地(di)(di)貌(mao)顯示出(chu)明顯的(de)三分(fen)特點，即盆西(xi)平原地(di)(di)貌(mao)、盆中丘陵地(di)(di)貌(mao)和(he)盆東(dong)山(shan)地(di)(di)地(di)(di)貌(mao)，三者(zhe)以龍泉山(shan)和(he)華(hua)鎣(ying)山(shan)為界。
四川盆地(di)其輪(lun)廓形態總體(ti)近(jin)似長方形，形似信(xin)封狀，右傾斜置在亞洲大陸，因此被地(di)理學者稱之為信(xin)封盆地(di)。信(xin)封盆地(di)東部(bu)(bu)頂(ding)點云(yun)陽（靠(kao)近(jin)萬州），南部(bu)(bu)頂(ding)點敘(xu)永(靠(kao)近(jin)遵義)，西部(bu)(bu)頂(ding)點雅安(an)，北(bei)部(bu)(bu)頂(ding)點廣元。信(xin)封盆地(di)幾(ji)(ji)何中(zhong)(zhong)(zhong)心城市遂(sui)寧（幾(ji)(ji)何中(zhong)(zhong)(zhong)心點大致(zhi)在蓬(peng)溪南部(bu)(bu)地(di)區），中(zhong)(zhong)(zhong)北(bei)部(bu)(bu)（內(nei)頂(ding)角）中(zhong)(zhong)(zhong)心城市南充，中(zhong)(zhong)(zhong)南部(bu)(bu)內(nei)頂(ding)角安(an)岳(yue)。
四川盆地西部的成都和(he)東南部的重慶皆為國(guo)家中心城市。
四川盆地(di)由(you)盆周(zhou)山(shan)地(di)和盆地(di)底部(bu)構成。
盆周東部(bu)為(wei)長江三峽(xia)，南部(bu)為(wei)云貴高原(yuan)(yuan)，西部(bu)為(wei)青(qing)藏高原(yuan)(yuan)，北部(bu)為(wei)大巴山。
盆地底部主要(yao)分為(wei)川東(dong)平(ping)行嶺谷(gu)、川中丘陵(ling)(ling)和(he)川西成都平(ping)原(yuan)三部分。龍(long)泉山(shan)是成都平(ping)原(yuan)和(he)川中丘陵(ling)(ling)的(de)界山(shan)，華鎣山(shan)是川中丘陵(ling)(ling)和(he)川東(dong)平(ping)行嶺谷(gu)的(de)界山(shan)。
（1）在龍(long)泉山(shan)和龍(long)門(men)山(shan)、邛崍山(shan)之(zhi)間的盆西(xi)平(ping)(ping)原(yuan)(yuan)，系斷裂下陷由岷(min)江(jiang)水系的河(he)流沖(chong)積(ji)而(er)成(cheng)(cheng)，面積(ji)約(yue)8000平(ping)(ping)方千米(mi)，為我國西(xi)南(nan)最大的平(ping)(ping)原(yuan)(yuan)，因成(cheng)(cheng)都(dou)(dou)位于平(ping)(ping)原(yuan)(yuan)之(zhi)中， 故稱(cheng)成(cheng)(cheng)都(dou)(dou)平(ping)(ping)原(yuan)(yuan)。成(cheng)(cheng)都(dou)(dou)平(ping)(ping)原(yuan)(yuan)海拔460米(mi)～750米(mi)，地勢由西(xi)北向東南(nan)傾斜，地表平(ping)(ping)坦，相對(dui)高差一般不超過30米(mi)～50米(mi)，它由岷(min)江(jiang)、沱江(jiang)、涪江(jiang)、青衣江(jiang)等(deng)八條河(he)流沖(chong)積(ji)聯綴而(er)成(cheng)(cheng)，土壤肥沃，河(he)渠稠(chou)密，有著(zhu)名的都(dou)(dou)江(jiang)堰自流灌溉，自古以(yi)來素(su)有“天(tian)府”之(zhi)稱(cheng)。
（2）在龍泉山(shan)(shan)和華鎣山(shan)(shan)之間的盆中丘(qiu)陵，地(di)勢(shi)低矮，海拔(ba)大多(duo)在300米(mi)～500米(mi)之間，相對(dui)高(gao)差50米(mi)～150米(mi)，地(di)勢(shi)由北向南(nan)傾斜，巖層近于水(shui)平，在流水(shui)的長期侵蝕切(qie)割作(zuo)(zuo)用(yong)下(xia)，形(xing)成臺階狀(zhuang)的方山(shan)(shan)丘(qiu)陵，南(nan)部(bu)多(duo)淺丘(qiu)，北部(bu)多(duo)深(shen)丘(qiu)。丘(qiu)陵地(di)表軟硬相間的紫紅色砂、頁巖極(ji)易風化為紫色土，富含(han)磷鉀，自然肥力較(jiao)高(gao)，宜種性廣，是四川全省糧食(shi)、經濟(ji)作(zuo)(zuo)物主產(chan)區。
（3）華鎣山以東(dong)為(wei)盆(pen)東(dong)平行(xing)嶺(ling)谷(gu)(gu)區(qu)(qu)，由多(duo)條(tiao)近東(dong)北西(xi)南走(zou)向(xiang)的條(tiao)狀背斜(xie)山地(di)(di)與向(xiang)斜(xie)寬谷(gu)(gu)組成，山地(di)(di)陡而窄(zhai)，高(gao)700米-1000米，其中，華鎣山高(gao)1705米，為(wei)盆(pen)地(di)(di)底部(bu)最高(gao)峰。山地(di)(di)頂部(bu)的石灰巖被雨水溶(rong)蝕后，常成凹槽(cao)，故(gu)山地(di)(di)大(da)多(duo)具(ju)有(you)“一山二嶺(ling)一槽(cao)”或(huo)“一山三嶺(ling)二槽(cao)”的特(te)色(se)。山嶺(ling)間的谷(gu)(gu)地(di)(di)寬而緩，海拔(ba)300米～500米，其間丘陵、平壩交錯分(fen)布(bu)，是平行(xing)嶺(ling)谷(gu)(gu)區(qu)(qu)工農業生(sheng)產主要(yao)地(di)(di)區(qu)(qu)。
四(si)川盆地(di)邊緣山地(di)區屬強烈(lie)上(shang)升的褶(zhe)皺(zhou)帶。
地(di)貌顯著特征是(shi)(shi)，海拔(ba)較高(gao)，過(guo)渡性明顯，均為一(yi)(yi)系列中山(shan)(shan)和低山(shan)(shan)所圍(wei)繞。盆地(di)北緣米(mi)(mi)倉(cang)山(shan)(shan)、大(da)巴山(shan)(shan)近(jin)東西(xi)(xi)走向，是(shi)(shi)秦巴山(shan)(shan)地(di)南翼部分，海拔(ba)一(yi)(yi)般在(zai)1500米(mi)(mi)～2200米(mi)(mi)之間(jian)，山(shan)(shan)勢(shi)(shi)雄偉，山(shan)(shan)坡陡峭，溝(gou)谷深切(qie)，相對高(gao)差(cha)可達(da)500米(mi)(mi)～1000米(mi)(mi)；南緣大(da)婁(lou)山(shan)(shan)屬(shu)氣勢(shi)(shi)磅礴的云貴高(gao)原(yuan)之一(yi)(yi)部分；西(xi)(xi)緣有龍門山(shan)(shan)、邛崍山(shan)(shan)、峨(e)眉(mei)山(shan)(shan)，山(shan)(shan)脊(ji)海拔(ba)都在(zai)1500米(mi)(mi)至～3000米(mi)(mi)以上(shang)，相對高(gao)差(cha)可達(da)1000米(mi)(mi)，屬(shu)中國(guo)(guo)地(di)勢(shi)(shi)第一(yi)(yi)級(ji)階梯。峨(e)眉(mei)山(shan)(shan)頂峰高(gao)3099米(mi)(mi)，與附近(jin)的平原(yuan)相對高(gao)差(cha)達(da)2660米(mi)(mi)，山(shan)(shan)勢(shi)(shi)巍(wei)峨(e)秀麗(li)，為中國(guo)(guo)四大(da)佛教名山(shan)(shan)之一(yi)(yi)。
四周為海拔2000～3000米的山(shan)(shan)(shan)脈和高(gao)原(yuan)所環繞(rao)，北面(mian)(mian)(mian)是(shi)大巴山(shan)(shan)(shan)、米倉(cang)山(shan)(shan)(shan)、龍門山(shan)(shan)(shan)，西面(mian)(mian)(mian)是(shi)青(qing)藏高(gao)原(yuan)邊緣的邛(qiong)崍山(shan)(shan)(shan)、大涼山(shan)(shan)(shan)，南面(mian)(mian)(mian)是(shi)大婁(lou)山(shan)(shan)(shan)，東面(mian)(mian)(mian)是(shi)巫山(shan)(shan)(shan)。
無論從(cong)構造還是人地(di)(di)(di)(di)(di)(di)貌(mao)上看(kan)，四川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)都是一個(ge)典型的(de)(de)(de)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)。它從(cong)震旦紀以(yi)來(lai)就是地(di)(di)(di)(di)(di)(di)殼比較穩定的(de)(de)(de)大(da)(da)型拗(ao)陷(xian)區(qu)。晚三(san)迭(die)紀的(de)(de)(de)印支運(yun)動中(zhong)成(cheng)(cheng)為(wei)(wei)(wei)一個(ge)內(nei)陸湖盆(pen)(pen)(pen)(pen)(pen)(pen)，但范圍(wei)要比今日的(de)(de)(de)四川(chuan)(chuan)大(da)(da)得多(duo)，中(zhong)生代堆(dui)積了(le)厚(hou)達3000～4000米的(de)(de)(de)紫紅色的(de)(de)(de)砂巖(yan)和(he)頁(ye)巖(yan)，因此人們又稱(cheng)(cheng)它為(wei)(wei)(wei)“紅色盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)”或“紫色盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)”。中(zhong)生代末期的(de)(de)(de)四川(chuan)(chuan)運(yun)動使盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)周圍(wei)褶(zhe)皺(zhou)成(cheng)(cheng)山，中(zhong)間相(xiang)對(dui)下(xia)陷(xian)，輪(lun)廓(kuo)基(ji)本形(xing)(xing)成(cheng)(cheng)，盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)內(nei)部(bu)地(di)(di)(di)(di)(di)(di)層也發生大(da)(da)規模的(de)(de)(de)變形(xing)(xing)。東(dong)(dong)部(bu)出現一組北東(dong)(dong)向的(de)(de)(de)褶(zhe)皺(zhou)，稱(cheng)(cheng)盆(pen)(pen)(pen)(pen)(pen)(pen)東(dong)(dong)褶(zhe)皺(zhou)帶；中(zhong)部(bu)形(xing)(xing)成(cheng)(cheng)穹(qiong)窿構造，稱(cheng)(cheng)盆(pen)(pen)(pen)(pen)(pen)(pen)中(zhong)穹(qiong)窿帶；西部(bu)表(biao)現成(cheng)(cheng)為(wei)(wei)(wei)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)沉陷(xian)帶，為(wei)(wei)(wei)今天盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)的(de)(de)(de)三(san)個(ge)地(di)(di)(di)(di)(di)(di)貌(mao)區(qu)奠定了(le)基(ji)礎(chu)。新生代的(de)(de)(de)喜馬拉雅運(yun)動使周圍(wei)山地(di)(di)(di)(di)(di)(di)再次上升(sheng)，盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)再次相(xiang)對(dui)下(xia)陷(xian)， 成(cheng)(cheng)都一帶下(xia)陷(xian)更深。同(tong)時，長江(jiang)切穿巫(wu)山，滾滾東(dong)(dong)流(liu)，完成(cheng)(cheng)了(le)統一的(de)(de)(de)長江(jiang)水(shui)系，使內(nei)流(liu)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)轉變為(wei)(wei)(wei)外流(liu)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)。四川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)可明顯分為(wei)(wei)(wei)邊緣山地(di)(di)(di)(di)(di)(di)和(he)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)底部(bu)兩大(da)(da)部(bu)分，其面積分別(bie)約為(wei)(wei)(wei)10萬(wan)多(duo)和(he)16萬(wan)多(duo)平方(fang)千米。 四川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)是我國最大(da)(da)的(de)(de)(de)外流(liu)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)，面積26萬(wan)多(duo)平方(fang)千米。四川(chuan)(chuan)盆(pen)(pen)(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)(di)內(nei)部(bu)丘(qiu)陵、平原交錯，地(di)(di)(di)(di)(di)(di)勢北高南低。由于地(di)(di)(di)(di)(di)(di)表(biao)形(xing)(xing)態的(de)(de)(de)不同(tong)，以(yi)華(hua)鎣山、龍(long)泉山為(wei)(wei)(wei)界(jie)。
盆底(di)可分(fen)為三部分(fen)：
①華鎣山以(yi)東(dong)(dong)為(wei)大致平行(xing)的(de)川東(dong)(dong)嶺谷，由東(dong)(dong)北—西南(nan)走向的(de)許多(duo)條(tiao)狀山體組成，海拔(ba)一(yi)般在700～800米，谷地(di)中(zhong)多(duo)低丘(qiu)與平壩，海拔(ba)200～500米，是(shi)川東(dong)(dong)農業和人(ren)口(kou)集中(zhong)的(de)地(di)方。
②華鎣山和龍泉(quan)山之(zhi)間為方(fang)山丘陵，即(ji)川(chuan)中丘陵。區內由于紫(zi)紅色砂頁巖傾角平(ping)緩(huan)，受切(qie)割后形(xing)成(cheng)大片方(fang)山式丘陵。海拔350～450米，相(xiang)對高度幾(ji)十米。當地(di)勞動人民利用方(fang)山山丘土層深厚的特點(dian)，把梯田一直修(xiu)到(dao)山頂(ding)。
③龍(long)泉山以(yi)西為平原。稱為川西平原或成(cheng)都(dou)平原，面積6000多(duo)平方千米，是四川盆地最大(da)的平原，也是西南地區(qu)最大(da)的平原，海拔約600米。
四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)屬(shu)揚子(zi)準(zhun)地(di)(di)(di)(di)(di)臺四(si)(si)川(chuan)臺坳。古生(sheng)(sheng)(sheng)代時(shi)相(xiang)對隆起(qi)，缺乏泥(ni)盆(pen)(pen)(pen)(pen)系和石(shi)(shi)炭系。印支運(yun)動(dong)轉換為(wei)(wei)(wei)大(da)(da)型拗陷，晚(wan)燕山(shan)(shan)(shan)運(yun)動(dong)，特(te)別(bie)是(shi)喜馬拉雅運(yun)動(dong)后(hou)發生(sheng)(sheng)(sheng)褶皺隆起(qi)。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)的(de)(de)格局(ju)主(zhu)要受北(bei)(bei)東—南西(xi)(xi)向(xiang)及(ji)北(bei)(bei)西(xi)(xi)向(xiang)兩條構造線控制，構成(cheng)了典型的(de)(de)菱(ling)形(xing)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)，四(si)(si)川(chuan)廣(guang)元、四(si)(si)川(chuan)雅安、四(si)(si)川(chuan)敘永為(wei)(wei)(wei)菱(ling)形(xing)的(de)(de)四(si)(si)頂點，東西(xi)(xi)兩邊(bian)(bian)稍(shao)長，為(wei)(wei)(wei)380～430公里，南北(bei)(bei)兩邊(bian)(bian)略(lve)短，為(wei)(wei)(wei)310～330公里。以(yi)上(shang)菱(ling)形(xing)四(si)(si)頂點的(de)(de)連(lian)線與(yu)(yu)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)內(nei)(nei)650～750米的(de)(de)等高線大(da)(da)體相(xiang)當，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)底(di)部(bu)與(yu)(yu)邊(bian)(bian)緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)也以(yi)此為(wei)(wei)(wei)分界。四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)在距今(jin)1.4億年以(yi)前，還是(shi)內(nei)(nei)陸湖(hu)(hu)盆(pen)(pen)(pen)(pen)。至距今(jin)6.6千(qian)萬年時(shi)，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)邊(bian)(bian)緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)迅速(su)隆升，長江中上(shang)游水系開(kai)始(shi)溝通。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)內(nei)(nei)湖(hu)(hu)水東瀉奠定了現今(jin)之(zhi)地(di)(di)(di)(di)(di)貌(mao)形(xing)態。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)邊(bian)(bian)緣(yuan)多低山(shan)(shan)(shan)和中山(shan)(shan)(shan)，山(shan)(shan)(shan)勢陡峻(jun)，發源盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)邊(bian)(bian)緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)的(de)(de)河(he)流大(da)(da)多為(wei)(wei)(wei)“V”型谷，嶺谷高差都逾500～1 000米， 地(di)(di)(di)(di)(di)表崎嶇，故(gu)歷(li)史上(shang)就有“蜀(shu)道難，難于上(shang)青天”之(zhi)說(shuo)。山(shan)(shan)(shan)脊海(hai)拔(ba)大(da)(da)多在2000～3000米，西(xi)(xi)北(bei)(bei)部(bu)與(yu)(yu)西(xi)(xi)部(bu)可(ke)超過3000～4000米，如龍門(men)山(shan)(shan)(shan)4984米，峨(e)眉(mei)山(shan)(shan)(shan)3099米，小相(xiang)嶺4 791米。地(di)(di)(di)(di)(di)表廣(guang)泛出露古生(sheng)(sheng)(sheng)代及(ji)其(qi)以(yi)前的(de)(de)石(shi)(shi)灰巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)，其(qi)次為(wei)(wei)(wei)板巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、片巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、結晶灰巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、石(shi)(shi)英(ying)巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、砂泥(ni)巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)和礫巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)，局(ju)部(bu)有花崗巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)和玄武巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)。石(shi)(shi)灰巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)分布區可(ke)見石(shi)(shi)林(lin)(lin)、溶(rong)洞、暗(an)河(he)、槽谷等喀斯特(te)地(di)(di)(di)(di)(di)貌(mao)，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)南緣(yuan)興文(wen)縣素(su)有“石(shi)(shi)林(lin)(lin)洞鄉”之(zhi)稱(cheng)(cheng)（見興文(wen)石(shi)(shi)林(lin)(lin)）。巫(wu)山(shan)(shan)(shan)十二峰和金佛山(shan)(shan)(shan)等名山(shan)(shan)(shan)主(zhu)要也由(you)(you)(you)石(shi)(shi)灰巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)發育而成(cheng)。由(you)(you)(you)石(shi)(shi)灰巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、玄武巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、花崗巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)等組成(cheng)的(de)(de)峨(e)眉(mei)山(shan)(shan)(shan)及(ji)由(you)(you)(you)砂泥(ni)巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)、礫巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)組成(cheng)的(de)(de)青城山(shan)(shan)(shan)，素(su)有“峨(e)眉(mei)天下(xia)秀”、“青城天下(xia)幽”之(zhi)稱(cheng)(cheng)，為(wei)(wei)(wei)中國(guo)著名游覽勝地(di)(di)(di)(di)(di)。盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)底(di)部(bu)海(hai)拔(ba)多數(shu)在250～700米，地(di)(di)(di)(di)(di)勢東南傾，盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)內(nei)(nei)各(ge)河(he)流均(jun)由(you)(you)(you)邊(bian)(bian)緣(yuan)山(shan)(shan)(shan)地(di)(di)(di)(di)(di)匯聚盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)底(di)部(bu)的(de)(de)長江干流，形(xing)成(cheng)向(xiang)心狀水系。地(di)(di)(di)(di)(di)表為(wei)(wei)(wei)大(da)(da)面積的(de)(de)中生(sheng)(sheng)(sheng)代紫紅色砂巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)與(yu)(yu)泥(ni)巖(yan)(yan)(yan)(yan)(yan)(yan)(yan)所覆(fu)蓋，故(gu)稱(cheng)(cheng)為(wei)(wei)(wei)“紅層盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)”，是(shi)中國(guo)中生(sheng)(sheng)(sheng)代陸相(xiang)紅層分布最集中地(di)(di)(di)(di)(di)區。四(si)(si)川(chuan)盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)為(wei)(wei)(wei)丘(qiu)陵性盆(pen)(pen)(pen)(pen)地(di)(di)(di)(di)(di)，底(di)部(bu)以(yi)丘(qiu)陵為(wei)(wei)(wei)主(zhu)，次為(wei)(wei)(wei)低山(shan)(shan)(shan)和平(ping)原。
四(si)川盆(pen)地(di)屬揚子(zi)陸臺(tai)一(yi)部分，稱(cheng)為(wei)四(si)川陸臺(tai)，屬較穩定的(de)(de)(de)(de)地(di)區，但仍經過(guo)兩次(ci)大規模(mo)的(de)(de)(de)(de)海(hai)浸。第一(yi)次(ci)從5億多年前的(de)(de)(de)(de)寒武(wu)紀(ji)開(kai)始，延續到3.7億多年的(de)(de)(de)(de)志留紀(ji)，不斷(duan)下陷成了(le)海(hai)洋盆(pen)地(di)，志留紀(ji)時發生加里東運(yun)動，除了(le)西部的(de)(de)(de)(de)龍門(men)山地(di)槽繼(ji)續下陷外，其余地(di)區上升為(wei)陸。2.7億年前的(de)(de)(de)(de)石炭紀(ji)末，發生范(fan)圍更(geng)大的(de)(de)(de)(de)第二次(ci)海(hai)浸，盆(pen)地(di)再次(ci)為(wei)海(hai)洋占據。二疊紀(ji)時海(hai)陸交替，形成重慶(qing)附(fu)近的(de)(de)(de)(de)南酮(tong)、松藻、天府(fu)等(deng)煤礦。二疊紀(ji)末，盆(pen)地(di)西部巖(yan)漿(jiang)噴出，峨(e)眉山小金頂及清音閣一(yi)帶的(de)(de)(de)(de)玄武(wu)巖(yan)就在這時生成。
距今1.9億(yi)年的(de)三(san)疊紀，“印支運動”使盆地(di)邊緣(yuan)逐(zhu)漸隆起成(cheng)(cheng)(cheng)山，被海(hai)水淹沒的(de)地(di)區(qu)逐(zhu)漸上升(sheng)成(cheng)(cheng)(cheng)陸，由海(hai)盆轉為湖盆。當時(shi)湖水幾乎(hu)占據現今四(si)川盆地(di)的(de)全境，稱(cheng)為“蜀湖”，從此(ci)結束了海(hai)浸的(de)歷史。在中生(sheng)代漫長(chang)的(de)1億(yi)多(duo)年里，盆地(di)氣候溫暖濕潤，到(dao)處生(sheng)長(chang)蕨類、蘇鐵和裸子植(zhi)物(wu)(wu)，是又一(yi)個(ge)成(cheng)(cheng)(cheng)煤期(qi)，永榮(rong)煤礦即(ji)在三(san)疊紀和侏羅(luo)紀時(shi)形成(cheng)(cheng)(cheng)。東起長(chang)壽、墊江，西(xi)到(dao)江油(you)、邛崍，北抵(di)大巴山麓，南到(dao)貴州(zhou)赤水，還是天然氣富集區(qu)。這一(yi)時(shi)期(qi)爬(pa)行動物(wu)(wu)恐(kong)龍稱(cheng)霸一(yi)時(shi)。1957年在合(he)州(zhou)發現的(de)“合(he)州(zhou)馬門溪龍”身長(chang)22米，高(gao)3.5米，是中國(guo)亞(ya)洲最大和最完整(zheng)的(de)恐(kong)龍化石。
7000萬(wan)年(nian)前(qian)(qian)的(de)(de)白堊紀末期，發(fa)(fa)(fa)生又一次(ci)強(qiang)(qiang)烈的(de)(de)地(di)(di)殼運(yun)(yun)動(dong)“燕山(shan)(shan)(shan)運(yun)(yun)動(dong)”。盆(pen)(pen)地(di)(di)四(si)(si)(si)周山(shan)(shan)(shan)地(di)(di)繼續隆(long)起，同時(shi)產(chan)生不(bu)(bu)少(shao)大(da)(da)斷層(ceng)(ceng)，如西部(bu)的(de)(de)龍(long)門山(shan)(shan)(shan)大(da)(da)斷層(ceng)(ceng)和東部(bu)的(de)(de)華(hua)瑩(ying)山(shan)(shan)(shan)大(da)(da)斷層(ceng)(ceng)，把盆(pen)(pen)地(di)(di)分(fen)為(wei)(wei)三部(bu)分(fen)。蜀(shu)(shu)湖(hu)(hu)縮小(xiao)為(wei)(wei)僅有2萬(wan)平(ping)方(fang)公里的(de)(de)蜀(shu)(shu)湖(hu)(hu)。封閉的(de)(de)盆(pen)(pen)地(di)(di)地(di)(di)形及急劇縮小(xiao)的(de)(de)水面，使氣候逐漸變(bian)得干熱(re)，沉積(ji)物由海(hai)(hai)(hai)相、海(hai)(hai)(hai)陸交替(ti)相變(bian)為(wei)(wei)陸相，大(da)(da)量風化(hua)、侵(qin)蝕、剝蝕的(de)(de)物質(zhi)在(zai)盆(pen)(pen)地(di)(di)堆(dui)積(ji)了(le)數千米(mi)厚，形成(cheng)紅色和紫(zi)紅色的(de)(de)砂(sha)、泥、頁巖。裸子植物不(bu)(bu)斷衰(shuai)退，恐龍(long)滅絕了(le)。內(nei)陸湖(hu)(hu)泊在(zai)干燥條件下(xia)，經(jing)強(qiang)(qiang)烈蒸(zheng)發(fa)(fa)(fa)，濃度增大(da)(da)，鹽(yan)分(fen)不(bu)(bu)斷積(ji)累，形成(cheng)鹽(yan)湖(hu)(hu)，后來泥沙掩(yan)埋而(er)保存(cun)于地(di)(di)層(ceng)(ceng)之中，經(jing)過漫長的(de)(de)地(di)(di)質(zhi)作用形成(cheng)巖層(ceng)(ceng)，自貢一帶(dai)是著(zhu)名的(de)(de)井(jing)鹽(yan)產(chan)地(di)(di)。 2000多萬(wan)年(nian)前(qian)(qian)的(de)(de)新第三紀，受喜馬拉(la)雅(ya)造山(shan)(shan)(shan)運(yun)(yun)動(dong)的(de)(de)影(ying)響。距今二、三百(bai)萬(wan)年(nian)的(de)(de)第四(si)(si)(si)紀，地(di)(di)殼再次(ci)發(fa)(fa)(fa)生構(gou)造運(yun)(yun)動(dong)。從而(er)，四(si)(si)(si)川(chuan)盆(pen)(pen)地(di)(di)由內(nei)流(liu)(liu)盆(pen)(pen)地(di)(di)變(bian)為(wei)(wei)外流(liu)(liu)陸盆(pen)(pen)，由封閉的(de)(de)內(nei)流(liu)(liu)區變(bian)為(wei)(wei)外流(liu)(liu)區，由以(yi)堆(dui)積(ji)為(wei)(wei)主(zhu)變(bian)為(wei)(wei)侵(qin)蝕為(wei)(wei)主(zhu)，經(jing)歷了(le)海(hai)(hai)(hai)盆(pen)(pen)——湖(hu)(hu)盆(pen)(pen)——陸盆(pen)(pen)的(de)(de)滄桑之變(bian)。 第四(si)(si)(si)紀是冰川(chuan)廣布的(de)(de)時(shi)代，盆(pen)(pen)地(di)(di)西北(bei)山(shan)(shan)(shan)地(di)(di)發(fa)(fa)(fa)育大(da)(da)量冰川(chuan)。冰川(chuan)消融(rong)后，大(da)(da)量沉積(ji)物由岷(min)江、沱江等攜(xie)帶(dai)，堆(dui)積(ji)在(zai)西部(bu)的(de)(de)凹陷(xian)區，即以(yi)前(qian)(qian)的(de)(de)蜀(shu)(shu)湖(hu)(hu)之中，最終形成(cheng)了(le)成(cheng)都平(ping)原。 四(si)(si)(si)川(chuan)盆(pen)(pen)地(di)(di)地(di)(di)貌豐富(fu)，平(ping)原7%，丘陵(ling)52%，低(di)山(shan)(shan)(shan)41%。
四(si)川(chuan)(chuan)盆地(di)(di)中植(zhi)物(wu)近萬(wan)種，古老而特(te)有種之多為中國其(qi)他地(di)(di)區所不及(ji)。在盆地(di)(di)邊緣山(shan)地(di)(di)及(ji)盆東平行嶺谷尚可(ke)見水杉(shan)(shan)、銀杉(shan)(shan)、鵝掌楸、檫木、三尖杉(shan)(shan)、珙桐、水青樹(shu)、連(lian)香樹(shu)、領春(chun)木、金錢(qian)槭(qi)、蠟梅、杜仲、紅(hong)豆杉(shan)(shan)、鐘萼木、福建柏(bo)、穗(sui)花杉(shan)(shan)、崖柏(bo)、木瓜(gua)紅(hong)等(deng)珍(zhen)稀(xi)孑(jie)遺植(zhi)物(wu)與特(te)有種。在濕(shi)熱(re)河谷可(ke)見桫(suo)欏(luo)、小羽桫(suo)欏(luo)、烏毛蕨、華(hua)南紫萁、里白(bai)等(deng)古熱(re)帶孑(jie)遺植(zhi)物(wu)。 四(si)川(chuan)(chuan)盆地(di)(di)的地(di)(di)帶性植(zhi)被是亞熱(re)帶常綠(lv)闊(kuo)葉(xie)(xie)林(lin)(lin)，其(qi)代表樹(shu)種有栲樹(shu)、峨(e)眉(mei)栲、刺果米(mi)(mi)櫧、青岡、曼青岡、包石櫟、華(hua)木荷(he)、大包木荷(he)、四(si)川(chuan)(chuan)大頭茶(cha)、楨楠、潤楠等(deng)，海拔一般情況下(xia)在1600～1 800米(mi)(mi)以下(xia)。其(qi)次(ci)有馬尾松(song)、杉(shan)(shan)木、柏(bo)木組成 的亞熱(re)帶針葉(xie)(xie)林(lin)(lin)及(ji)竹林(lin)(lin)。 邊緣山(shan)地(di)(di)從下(xia)而上是常綠(lv)闊(kuo)葉(xie)(xie)林(lin)(lin)、常綠(lv)闊(kuo)葉(xie)(xie)與落葉(xie)(xie)闊(kuo)葉(xie)(xie)混(hun)交林(lin)(lin)，寒(han)溫帶山(shan)地(di)(di)針葉(xie)(xie)林(lin)(lin)，局部(bu)有亞高山(shan)灌叢草(cao)甸。
四川盆(pen)地(di)(di)是(shi)中(zhong)(zhong)國動(dong)物(wu)種類最多(duo)、最齊全的(de)(de)地(di)(di)區之(zhi)一(yi)。據統計(ji)，除魚類外，盆(pen)地(di)(di)底(di)部共有(you)動(dong)物(wu)417種，盆(pen)地(di)(di)西(xi)緣(yuan)、北緣(yuan)和南緣(yuan)山(shan)地(di)(di)分別為487種、317種與(yu)288種，其中(zhong)(zhong)經(jing)濟(ji)動(dong)物(wu)均占一(yi)半以上。盆(pen)地(di)(di)西(xi)緣(yuan)山(shan)地(di)(di)是(shi)中(zhong)(zhong)國特有(you)而古(gu)老動(dong)物(wu)保存(cun)最好、最集(ji)中(zhong)(zhong)的(de)(de)地(di)(di)區，屬于(yu)一(yi)類保護動(dong)物(wu)的(de)(de)有(you)大(da)熊(xiong)貓(mao)、金(jin)絲(si)猴(hou)(hou)、扭角羚、灰金(jin)絲(si)猴(hou)(hou)、白(bai)唇鹿等(deng)。還有(you)珍貴(gui)特有(you)動(dong)物(wu)小熊(xiong)貓(mao)、雪豹、鬣羚、短尾(wei)猴(hou)(hou)、獼猴(hou)(hou)、毛冠鹿、水獺及鴛鴦、血雉(zhi)、紅腹(fu)角雉(zhi)、綠尾(wei)虹雉(zhi)、白(bai)腹(fu)錦雞(ji)、紅腹(fu)錦雞(ji)等(deng)。 盆(pen)地(di)(di)西(xi)緣(yuan)的(de)(de)平武(wu)(wu)、青(qing)川、北川、寶興、天全、洪雅、馬(ma)(ma)邊等(deng)地(di)(di)，均為中(zhong)(zhong)國大(da)熊(xiong)貓(mao)的(de)(de)主(zhu)要分布區。已(yi)設(she)立唐家(jia)河(he)、王朗(lang)、臥(wo)龍（見(jian)臥(wo)龍自然保護區）、蜂桶寨(zhai)、喇叭河(he)等(deng)7處大(da)熊(xiong)貓(mao)、金(jin)絲(si)猴(hou)(hou)等(deng)自然保護區。 酉陽(yang)、馬(ma)(ma)邊、平武(wu)(wu)等(deng)盆(pen)地(di)(di)邊緣(yuan)山(shan)地(di)(di)溪溝中(zhong)(zhong)的(de)(de)大(da)鯢及長江(jiang)、金(jin)沙江(jiang)中(zhong)(zhong)的(de)(de)中(zhong)(zhong)華(hua)鱘、白(bai)鱘也為四川所(suo)特有(you)，均屬國家(jia)保護動(dong)物(wu)。
四川(chuan)盆地有煤(mei)、鐵、天然氣、石油(you)、鹽、芒硝(xiao)、石膏、磷、硫、鋁、金、銅(tong)、錳、石墨、汞(gong)等礦(kuang)產(chan)資(zi)源，其中天然氣、芒硝(xiao)為全(quan)中國之(zhi)冠，并有中國重要的鍶礦(kuang)。川(chuan)東北是世界(jie)最大的天然氣富集區之(zhi)一，川(chuan)中和南充等地鹽巖礦(kuang)儲量很大。
四川(chuan)盆(pen)地地形閉塞(sai)，由于(yu)(yu)北部(bu)秦嶺阻擋冷空(kong)氣，冬(dong)季氣溫(wen)高于(yu)(yu)同緯度(du)其他(ta)地區。最冷月北部(bu)均溫(wen)3～5℃，南部(bu)5~8℃，較(jiao)同緯度(du)的上海(hai)、湖北、安徽(hui)及緯度(du)偏南的貴州(zhou)高1～4℃。盆(pen)地北部(bu)極(ji)端最低(di)(di)溫(wen)-8～-5℃，南部(bu)-5℃~-2℃。霜雪少見，年(nian)無霜期長280～350天，同緯度(du)上的武(wu)漢冬(dong)天卻霜雪不斷，盆(pen)地位于(yu)(yu)長江(jiang)河谷中的長寧(ning)全年(nian)無霜。 盆(pen)地各地夏季始于(yu)(yu)5月底，終(zhong)于(yu)(yu)9月中旬，夏長4個月，溫(wen)度(du)上東高西(xi)低(di)(di)。盆(pen)地西(xi)部(bu)夏天平(ping)均氣溫(wen)約25℃，較(jiao)同緯度(du)的上海(hai)、武(wu)漢等城市(shi)偏低(di)(di)3-4度(du)，但濕度(du)較(jiao)大，所以悶(men)熱難忍。
東(dong)部(bu)最熱(re)月(yue)氣溫(wen)高(gao)(gao)(gao)達26～29℃，長(chang)江河谷局地(di)(di)(di)(di)達到30℃。盛(sheng)夏(xia)連晴高(gao)(gao)(gao)溫(wen)天氣又造成盆地(di)(di)(di)(di)東(dong)南部(bu)嚴重的(de)夏(xia)伏旱。盆地(di)(di)(di)(di)氣溫(wen)東(dong)南高(gao)(gao)(gao)西北(bei)低，盆底(di)高(gao)(gao)(gao)邊緣低； 各地(di)(di)(di)(di)年均溫(wen)16～18℃。10℃以(yi)上(shang)活(huo)(huo)動(dong)積(ji)(ji)溫(wen)4500～6000℃，持續期8～9個月(yue)，屬(shu)中亞熱(re)帶。東(dong)南部(bu)的(de)長(chang)江河谷積(ji)(ji)溫(wen)超過(guo)6000℃，相(xiang)當于中國南嶺以(yi)南的(de)南亞熱(re)帶氣候。盆地(di)(di)(di)(di)氣溫(wen)東(dong)高(gao)(gao)(gao)西低，南高(gao)(gao)(gao)北(bei)低，盆底(di)高(gao)(gao)(gao)而邊緣低，等(deng)溫(wen)線(xian)分(fen)布呈現同心(xin)圓狀(zhuang)。盆地(di)(di)(di)(di)邊緣山地(di)(di)(di)(di)氣溫(wen)具有垂直(zhi)分(fen)布特點，如峨(e)眉(mei)山、金佛(fo)山海拔(ba)升高(gao)(gao)(gao)百(bai)米，氣溫(wen)遞減0.55℃和0.61℃。峨(e)眉(mei)山頂年均溫(wen)僅3℃，10℃以(yi)上(shang)活(huo)(huo)動(dong)積(ji)(ji)溫(wen)586℃，氣候上(shang)相(xiang)當于寒(han)溫(wen)帶和亞寒(han)帶。
四川盆地(di)年降(jiang)水(shui)量(liang)1000～1300毫(hao)米，盆地(di)邊緣(yuan)山(shan)(shan)(shan)(shan)地(di)降(jiang)水(shui)十分(fen)充沛，如(ru)樂山(shan)(shan)(shan)(shan)和雅安(an)間(jian)的西(xi)緣(yuan)山(shan)(shan)(shan)(shan)地(di)年降(jiang)水(shui)量(liang)為(wei)(wei)1 500～1800毫(hao)米，為(wei)(wei)中(zhong)國突出的多雨(yu)區，有“華(hua)西(xi)雨(yu)屏”之(zhi)稱。但(dan)冬干、春旱、夏澇、秋綿雨(yu)，年內分(fen)配不均，70～75%的雨(yu)量(liang)集中(zhong)于6～10月。最大日降(jiang)水(shui)量(liang)可達300～500毫(hao)米。“巴山(shan)(shan)(shan)(shan)夜雨(yu)”自古聞名，夜雨(yu)占總雨(yu)量(liang)的60～70%以(yi)上。盆地(di)區霧大濕重(zhong)，云低陰天多。峨眉山(shan)(shan)(shan)(shan)、金佛山(shan)(shan)(shan)(shan)是中(zhong)國霧日最多地(di)區之(zhi)一，年相(xiang)對濕度之(zhi)高也(ye)為(wei)(wei)中(zhong)國之(zhi)冠。盆地(di)年日照僅900～1300小(xiao)時，年太陽(yang)輻射量(liang)為(wei)(wei)370～420千焦耳/平方厘米，均為(wei)(wei)中(zhong)國最低值(zhi)，故有“蜀犬吠日”之(zhi)說。
