印(yin)度(du)洋在古(gu)代稱為“厄立特(te)里(li)(li)亞海”，早見于古(gu)希臘地(di)(di)理(li)學家希羅多德（前484-前425年(nian)）所著(zhu)《歷史》一書及(ji)其編繪的世界(jie)地(di)(di)圖中。“厄里(li)(li)特(te)里(li)(li)亞”（ERYTHREA）希臘文原意為紅色，全名意為紅海。
“印(yin)度洋”這(zhe)一名稱相(xiang)對出現得較晚。公(gong)元1世紀(ji)后(hou)期的(de)羅馬地理學(xue)家彭波尼(ni)烏斯·梅拉可能是早使(shi)用此(ci)名的(de)人。公(gong)元10世紀(ji)，阿拉伯人伊本·豪卡勒(le)編繪的(de)世界地圖上也使(shi)用了(le)這(zhe)個名字。
近代(dai)正式使用印度洋(yang)(yang)一名則是(shi)在(zai)1515年左右，當時中(zhong)歐地圖學家舍納爾編繪的(de)地圖上，把這片大洋(yang)(yang)標(biao)注為“東(dong)方(fang)(fang)的(de)印度洋(yang)(yang)”，此處(chu)的(de)“東(dong)方(fang)(fang)”一詞是(shi)與大西(xi)洋(yang)(yang)相對(dui)而言的(de)。
1497年(nian)，葡萄牙(ya)航(hang)(hang)海家達·伽馬東(dong)航(hang)(hang)尋找(zhao)印度，便將沿途所經過的洋(yang)面統(tong)稱(cheng)之為印度洋(yang)。
1570年奧爾太(tai)利烏斯編繪的世界(jie)地圖(tu)集中，把“東方(fang)的印度洋”一名(ming)去(qu)掉“東方(fang)的”，簡(jian)化為“印度洋”。這個名(ming)字逐漸被人們(men)接受，成為通用的稱呼。
印(yin)度(du)(du)(du)洋是(shi)聯(lian)系亞(ya)洲、非洲和(he)(he)大洋洲之間的(de)(de)(de)交(jiao)通要道(dao)。從印(yin)度(du)(du)(du)洋往西(xi)北(bei)通過(guo)曼德海(hai)(hai)峽、紅(hong)海(hai)(hai)；蘇伊士運(yun)河、地中(zhong)海(hai)(hai)和(he)(he)直布羅(luo)陀(tuo)海(hai)(hai)峽到達西(xi)歐(ou)；向(xiang)(xiang)西(xi)南經(jing)好(hao)望角(jiao)進(jin)入(ru)大西(xi)洋，通向(xiang)(xiang)歐(ou)美沿(yan)(yan)海(hai)(hai)各地；向(xiang)(xiang)東(dong)北(bei)經(jing)馬六甲海(hai)(hai)峽和(he)(he)龍目海(hai)(hai)峽進(jin)入(ru)太平洋。印(yin)度(du)(du)(du)洋沿(yan)(yan)岸是(shi)世界資源(yuan)的(de)(de)(de)一(yi)個重要出口(kou)地，沿(yan)(yan)岸各國出口(kou)的(de)(de)(de)石油、礦砂、橡(xiang)膠(jiao)、棉花、糧食和(he)(he)進(jin)口(kou)的(de)(de)(de)水(shui)泥、機械產品和(he)(he)化工(gong)產品等(deng)大宗貨物都需要依(yi)靠廉價(jia)的(de)(de)(de)海(hai)(hai)洋運(yun)輸，再加上大量(liang)(liang)的(de)(de)(de)過(guo)境運(yun)輸，使印(yin)度(du)(du)(du)洋有較大的(de)(de)(de)運(yun)輸量(liang)(liang)，擁有世界l/6的(de)(de)(de)貨物吞吐量(liang)(liang)和(he)(he)近1/10的(de)(de)(de)貨物周(zhou)轉量(liang)(liang)。
印(yin)(yin)度(du)洋(yang)的(de)(de)航(hang)(hang)運(yun)業雖(sui)不如(ru)大西(xi)洋(yang)和太平洋(yang)發(fa)達，但(dan)由于(yu)中(zhong)東(dong)地區(qu)盛產(chan)的(de)(de)石(shi)油(you)(you)通過印(yin)(yin)度(du)洋(yang)航(hang)(hang)線(xian)(xian)源源不斷向(xiang)外輸(shu)出(chu)，因(yin)而(er)印(yin)(yin)度(du)洋(yang)航(hang)(hang)線(xian)(xian)在世界(jie)(jie)上占有(you)重要(yao)(yao)的(de)(de)地位(wei)。印(yin)(yin)度(du)洋(yang)上運(yun)輸(shu)石(shi)油(you)(you)的(de)(de)航(hang)(hang)線(xian)(xian)有(you)兩條(tiao)：一(yi)條(tiao)是(shi)(shi)出(chu)波斯灣(wan)向(xiang)西(xi)，繞過南非(fei)的(de)(de)好望(wang)角或(huo)者通過紅海(hai)、蘇伊(yi)士運(yun)河，到歐洲和美國(guo)。這是(shi)(shi)世界(jie)(jie)上重要(yao)(yao)的(de)(de)石(shi)油(you)(you)運(yun)輸(shu)線(xian)(xian)。一(yi)條(tiao)是(shi)(shi)出(chu)波斯灣(wan)向(xiang)東(dong)，穿過馬(ma)六甲(jia)海(hai)峽(xia)(xia)或(huo)龍(long)目海(hai)峽(xia)(xia)到日本和東(dong)亞其他國(guo)家。霍爾木茲海(hai)峽(xia)(xia)在印(yin)(yin)度(du)洋(yang)航(hang)(hang)線(xian)(xian)上占有(you)重要(yao)(yao)地位(wei)，波斯灣(wan)地區(qu)出(chu)口石(shi)油(you)(you)總量90%從此海(hai)峽(xia)(xia)運(yun)出(chu)，因(yin)而(er)霍爾木茲海(hai)峽(xia)(xia)被稱(cheng)為(wei)“石(shi)油(you)(you)海(hai)峽(xia)(xia)”。蘇伊(yi)士運(yun)河經馬(ma)六甲(jia)海(hai)峽(xia)(xia)的(de)(de)航(hang)(hang)線(xian)(xian)，是(shi)(shi)印(yin)(yin)度(du)洋(yang)東(dong)西(xi)間一(yi)條(tiao)重要(yao)(yao)的(de)(de)航(hang)(hang)道，運(yun)輸(shu)量巨大，它(ta)將西(xi)歐、地中(zhong)海(hai)沿岸各(ge)國(guo)的(de)(de)經濟與(yu)遠東(dong)及北美洲西(xi)海(hai)岸各(ge)國(guo)的(de)(de)經濟緊密地聯系起來。
印度(du)(du)洋(yang)(yang)的(de)地理位置非常重要(yao)(yao)，是溝通(tong)(tong)(tong)亞(ya)洲(zhou)(zhou)、非洲(zhou)(zhou)、歐洲(zhou)(zhou)和大洋(yang)(yang)洲(zhou)(zhou)的(de)交通(tong)(tong)(tong)要(yao)(yao)道。向(xiang)(xiang)東通(tong)(tong)(tong)過馬六甲(jia)海(hai)峽可以(yi)進(jin)入(ru)(ru)太平洋(yang)(yang)，向(xiang)(xiang)西(xi)繞過好望角(jiao)可達大西(xi)洋(yang)(yang)，向(xiang)(xiang)西(xi)北通(tong)(tong)(tong)過紅海(hai)、蘇伊士(shi)運河，可入(ru)(ru)地中海(hai)。航(hang)線(xian)主要(yao)(yao)由亞(ya)、歐航(hang)線(xian)和南亞(ya)、東南亞(ya)、南非、大洋(yang)(yang)洲(zhou)(zhou)之間的(de)航(hang)線(xian)。印度(du)(du)洋(yang)(yang)的(de)海(hai)底電纜多分布在北部，重要(yao)(yao)的(de)線(xian)路有亞(ya)丁(ding)—孟買—馬德拉(la)斯—新(xin)加坡線(xian)；亞(ya)丁(ding)—科(ke)倫坡線(xian)；東非沿(yan)岸線(xian)。塞舌爾群(qun)島的(de)馬埃島、毛(mao)里求斯島和科(ke)科(ke)斯群(qun)島是主要(yao)(yao)的(de)海(hai)底電纜樞(shu)紐站(zhan)。沿(yan)岸港口終年不凍，四(si)季通(tong)(tong)(tong)航(hang)。
印(yin)度洋西南(nan)(nan)以通過(guo)南(nan)(nan)非厄加勒(le)斯特的經(jing)線同大西洋分界(jie)，東南(nan)(nan)以通過(guo)塔斯馬尼亞島東南(nan)(nan)角(jiao)至南(nan)(nan)極大陸(lu)的經(jing)線與(yu)太平(ping)洋聯結。印(yin)度洋的輪廓為北部為陸(lu)地封閉(bi)，南(nan)(nan)面(mian)則以南(nan)(nan)緯60°為界(jie)，與(yu)南(nan)(nan)冰洋相(xiang)連。
印度洋的主要屬海(hai)和海(hai)灣(wan)(wan)是紅海(hai)、阿拉(la)伯海(hai)、亞(ya)丁灣(wan)(wan)、波斯(si)灣(wan)(wan)、阿曼(man)灣(wan)(wan)、孟加拉(la)灣(wan)(wan)、安達(da)曼(man)海(hai)、阿拉(la)弗(fu)拉(la)海(hai)、帝汶海(hai)、卡奔塔利亞(ya)灣(wan)(wan)、大(da)澳大(da)利亞(ya)灣(wan)(wan)、莫(mo)桑比克海(hai)峽等等。
印度洋有很多島(dao)(dao)嶼，其中大部分是(shi)大陸島(dao)(dao)，如(ru)馬(ma)達(da)加斯(si)(si)加島(dao)(dao)、斯(si)(si)里蘭卡島(dao)(dao)、安(an)達(da)曼群島(dao)(dao)、尼(ni)科巴群島(dao)(dao)、明打威(wei)群島(dao)(dao)等。留尼(ni)汪島(dao)(dao)、科摩羅群島(dao)(dao)、阿姆斯(si)(si)特(te)丹島(dao)(dao)、克羅澤群島(dao)(dao)、凱(kai)爾蓋朗(lang)群島(dao)(dao)為(wei)火山島(dao)(dao)。拉克沙群島(dao)(dao)、馬(ma)爾代夫(fu)群島(dao)(dao)、查戈(ge)斯(si)(si)群島(dao)(dao)，以及爪哇(wa)西南的圣誕島(dao)(dao)、科科斯(si)(si)群島(dao)(dao)都是(shi)珊瑚(hu)島(dao)(dao)，馬(ma)達(da)加斯(si)(si)加島(dao)(dao)是(shi)南回歸線穿過的島(dao)(dao)。
印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)底(di)地貌錯綜(zong)復(fu)雜(za)，除洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)底(di)中(zhong)(zhong)(zhong)(zhong)部(bu)有(you)呈“入”字形(xing)的(de)(de)大(da)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)(zhong)(zhong)脊外，東(dong)(dong)(dong)部(bu)尚有(you)東(dong)(dong)(dong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)和(he)島(dao)弧、海(hai)(hai)(hai)溝(gou)帶，在(zai)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)、海(hai)(hai)(hai)丘、海(hai)(hai)(hai)臺之間分(fen)(fen)布著許多海(hai)(hai)(hai)盆(pen)。印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)的(de)(de)大(da)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)(zhong)(zhong)脊，包括(kuo)中(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)、阿拉伯一(yi)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)、西(xi)南(nan)(nan)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)和(he)東(dong)(dong)(dong)南(nan)(nan)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)。中(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)°嶺(ling)(ling)(ling)(ling)從阿姆斯特(te)丹島(dao)向(xiang)(xiang)(xiang)北(bei)延(yan)(yan)伸，一(yi)般(ban)高于(yu)兩側海(hai)(hai)(hai)盆(pen)1300-2500米，平均寬度(du)(du)(du)(du)(du)(du)(du)(du)達(da)800千(qian)米左右，由于(yu)被(bei)一(yi)些(xie)與(yu)之垂直或(huo)斜交的(de)(de)斷(duan)裂帶切斷(duan)錯開(kai)，中(zhong)(zhong)(zhong)(zhong)脊裂谷(gu)表現時(shi)斷(duan)時(shi)續的(de)(de)特(te)征，因此中(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)形(xing)態(tai)崎(qi)嶇破碎。中(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)向(xiang)(xiang)(xiang)西(xi)北(bei)延(yan)(yan)伸形(xing)成(cheng)(cheng)阿拉伯一(yi)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)，高度(du)(du)(du)(du)(du)(du)(du)(du)較(jiao)大(da)，繼續向(xiang)(xiang)(xiang)西(xi)北(bei)延(yan)(yan)伸，進入亞丁灣和(he)紅海(hai)(hai)(hai)；中(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)從羅德里格斯島(dao)向(xiang)(xiang)(xiang)西(xi)南(nan)(nan)分(fen)(fen)出西(xi)南(nan)(nan)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)，經愛德華(hua)太子(zi)群(qun)島(dao)，接大(da)西(xi)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)一(yi)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)；中(zhong)(zhong)(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)至圣波爾島(dao)向(xiang)(xiang)(xiang)東(dong)(dong)(dong)南(nan)(nan)連接東(dong)(dong)(dong)南(nan)(nan)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)，再向(xiang)(xiang)(xiang)東(dong)(dong)(dong)連接太平洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)一(yi)南(nan)(nan)極海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)和(he)東(dong)(dong)(dong)太平洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)。印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)底(di)除中(zhong)(zhong)(zhong)(zhong)脊海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)外，還有(you)許多近似南(nan)(nan)北(bei)向(xiang)(xiang)(xiang)的(de)(de)構(gou)造(zao)帶。這些(xie)構(gou)造(zao)帶相(xiang)互平行，綿(mian)延(yan)(yan)很(hen)遠(yuan)，其中(zhong)(zhong)(zhong)(zhong)東(dong)(dong)(dong)印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)，走向(xiang)(xiang)(xiang)與(yu)東(dong)(dong)(dong)經90°經線一(yi)致(zhi)，是世界上(shang)較(jiao)直的(de)(de)一(yi)條(tiao)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)。它北(bei)起北(bei)緯10°附近的(de)(de)安達(da)曼群(qun)島(dao)，南(nan)(nan)至南(nan)(nan)緯3l° 的(de)(de)斷(duan)裂海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)，長約(yue)5 000千(qian)米，東(dong)(dong)(dong)西(xi)寬約(yue)150-250千(qian)米。由于(yu)它沿(yan)著東(dong)(dong)(dong)經90°分(fen)(fen)布，故又叫(jiao)東(dong)(dong)(dong)經90° 海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)或(huo)卡彭(peng)特(te)海(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)。大(da)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)(zhong)(zhong)脊呈“入”字形(xing)，將印(yin)(yin)(yin)(yin)(yin)度(du)(du)(du)(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)(yang)分(fen)(fen)成(cheng)(cheng)三個海(hai)(hai)(hai)域。
印(yin)度(du)(du)洋(yang)屬海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)較(jiao)(jiao)少(shao)。內海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)有(you)(you)(you)紅海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)和(he)(he)(he)波斯(si)灣(wan)；邊緣(yuan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)有(you)(you)(you)西(xi)北(bei)(bei)部(bu)(bu)的(de)阿(a)拉(la)(la)伯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)，東北(bei)(bei)部(bu)(bu)的(de)安(an)達曼(man)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)，東部(bu)(bu)的(de)帝汶海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)和(he)(he)(he)阿(a)拉(la)(la)弗拉(la)(la)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)；大(da)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)灣(wan)有(you)(you)(you)西(xi)北(bei)(bei)部(bu)(bu)的(de)亞(ya)丁灣(wan)和(he)(he)(he)阿(a)曼(man)灣(wan)，東北(bei)(bei)部(bu)(bu)的(de)孟加拉(la)(la)灣(wan)，澳(ao)大(da)利(li)(li)亞(ya)北(bei)(bei)面的(de)卡奔塔(ta)利(li)(li)亞(ya)灣(wan)（Carpentaria）、南(nan)面的(de)大(da)澳(ao)大(da)利(li)(li)亞(ya)灣(wan)。在南(nan)極洲海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)域也有(you)(you)(you)一些屬海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)。海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)岸(an)線除北(bei)(bei)部(bu)(bu)比較(jiao)(jiao)曲(qu)折(zhe)之外，大(da)部(bu)(bu)分平(ping)直，少(shao)島(dao)(dao)(dao)嶼。大(da)島(dao)(dao)(dao)有(you)(you)(you)馬達加斯(si)加島(dao)(dao)(dao)、索科(ke)特拉(la)(la)（Socotra）島(dao)(dao)(dao)、斯(si)里蘭卡島(dao)(dao)(dao)，還(huan)有(you)(you)(you)塞(sai)席爾群(qun)(qun)島(dao)(dao)(dao)；火山島(dao)(dao)(dao)有(you)(you)(you)科(ke)摩羅（Comoros）群(qun)(qun)島(dao)(dao)(dao)、馬斯(si)克林(lin)（Mascarene）群(qun)(qun)島(dao)(dao)(dao)和(he)(he)(he)凱爾蓋(gai)朗（Kerguelen）群(qun)(qun)島(dao)(dao)(dao)；珊瑚島(dao)(dao)(dao)有(you)(you)(you)馬爾代夫群(qun)(qun)島(dao)(dao)(dao)。大(da)陸邊緣(yuan)地帶包括大(da)陸棚(peng)和(he)(he)(he)大(da)陸坡。大(da)陸棚(peng)一般(ban)比較(jiao)(jiao)狹窄，大(da)陸棚(peng)較(jiao)(jiao)寬的(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)域有(you)(you)(you)阿(a)拉(la)(la)伯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)、安(an)達曼(man)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)、孟加拉(la)(la)灣(wan)和(he)(he)(he)大(da)澳(ao)大(da)利(li)(li)亞(ya)灣(wan)，寬處在澳(ao)大(da)利(li)(li)亞(ya)至新幾內亞(ya)島(dao)(dao)(dao)之間，約965千米。大(da)陸坡陡峻之處坡度(du)(du)10°-30°，一般(ban)坡度(du)(du)較(jiao)(jiao)小(xiao)。在印(yin)度(du)(du)河、恒河入(ru)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)口外的(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)域，有(you)(you)(you)面積(ji)寬廣的(de)水(shui)下(xia)沖積(ji)扇，被(bei)水(shui)下(xia)峽谷所切(qie)割。
島(dao)(dao)(dao)(dao)弧(hu)帶(dai)從(cong)緬甸(dian)至(zhi)澳(ao)大(da)利(li)亞(ya)(ya)延(yan)伸(shen)達(da)5150千(qian)米(mi)(mi)(mi)，可(ke)分(fen)為(wei)兩列平行(xing)的(de)(de)(de)島(dao)(dao)(dao)(dao)鏈：內弧(hu)屬火山島(dao)(dao)(dao)(dao)，有(you)大(da)、小巽他群(qun)(qun)島(dao)(dao)(dao)(dao)（包括蘇門答(da)臘島(dao)(dao)(dao)(dao)、爪(zhua)哇(wa)島(dao)(dao)(dao)(dao)、帝汶島(dao)(dao)(dao)(dao)等）；外弧(hu)為(wei)非(fei)火山島(dao)(dao)(dao)(dao)，有(you)安達(da)曼群(qun)(qun)島(dao)(dao)(dao)(dao)、尼(ni)科巴（Nicobar）群(qun)(qun)島(dao)(dao)(dao)(dao)、明打威（Mentawai）群(qun)(qun)島(dao)(dao)(dao)(dao)等。島(dao)(dao)(dao)(dao)弧(hu)的(de)(de)(de)外緣——爪(zhua)哇(wa)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)溝為(wei)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)水(shui)域，深點7450米(mi)(mi)(mi)。印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)中(zhong)(zhong)央(yang)的(de)(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)可(ke)分(fen)為(wei)3支：北(bei)(bei)支為(wei)阿(a)(a)(a)(a)拉伯(bo)(bo)——印(yin)(yin)(yin)(yin)(yin)(yin)度(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)；西(xi)(xi)南(nan)(nan)(nan)支為(wei)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)西(xi)(xi)南(nan)(nan)(nan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)，它與大(da)西(xi)(xi)洋(yang)(yang)——印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)相連；東(dong)(dong)(dong)南(nan)(nan)(nan)支為(wei)中(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)，它與印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)東(dong)(dong)(dong)南(nan)(nan)(nan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)相接。北(bei)(bei)支海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)和(he)(he)西(xi)(xi)南(nan)(nan)(nan)支海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)是結構復雜的(de)(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)底(di)(di)山脈，寬度(du)400-970千(qian)米(mi)(mi)(mi)，相對高度(du)1830-3050米(mi)(mi)(mi)，海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)的(de)(de)(de)中(zhong)(zhong)脊為(wei)裂(lie)谷帶(dai)，地(di)貌極(ji)為(wei)崎嶇(qu)險峻；東(dong)(dong)(dong)南(nan)(nan)(nan)支海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)從(cong)中(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)至(zhi)阿(a)(a)(a)(a)姆斯(si)特丹島(dao)(dao)(dao)(dao)的(de)(de)(de)寬度(du)達(da)1450千(qian)米(mi)(mi)(mi)，裂(lie)谷很(hen)少(shao)。印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)中(zhong)(zhong)央(yang)的(de)(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)被大(da)小不(bu)一的(de)(de)(de)斷(duan)(duan)裂(lie)帶(dai)所切(qie)割，例如歐文斷(duan)(duan)裂(lie)帶(dai)，即延(yan)伸(shen)至(zhi)阿(a)(a)(a)(a)拉伯(bo)(bo)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)和(he)(he)索(suo)馬利(li)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)，海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)底(di)(di)巖層位移達(da)320千(qian)米(mi)(mi)(mi)。印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)東(dong)(dong)(dong)部(bu)(bu)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)域1962年發現的(de)(de)(de)東(dong)(dong)(dong)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)（或稱(cheng)「東(dong)(dong)(dong)經九十度(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)」），南(nan)(nan)(nan)北(bei)(bei)直線(xian)延(yan)伸(shen)約4990千(qian)米(mi)(mi)(mi)，為(wei)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)中(zhong)(zhong)較長較直的(de)(de)(de)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)。海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)之間為(wei)一系(xi)列海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)︰北(bei)(bei)部(bu)(bu)和(he)(he)西(xi)(xi)北(bei)(bei)部(bu)(bu)有(you)阿(a)(a)(a)(a)拉伯(bo)(bo)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)、索(suo)馬利(li)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)；中(zhong)(zhong)部(bu)(bu)自(zi)西(xi)(xi)而東(dong)(dong)(dong)，有(you)馬達(da)加斯(si)加海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)、中(zhong)(zhong)印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)、科科斯(si)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)和(he)(he)北(bei)(bei)澳(ao)大(da)利(li)亞(ya)(ya)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)；南(nan)(nan)(nan)部(bu)(bu)重要的(de)(de)(de)是克羅澤（Crozet）海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)。根據大(da)陸漂移學說，印(yin)(yin)(yin)(yin)(yin)(yin)度(du)洋(yang)(yang)是在(zai)中(zhong)(zhong)生代（距今6500萬(wan)(wan)-22500萬(wan)(wan)年前）南(nan)(nan)(nan)半球貢德(de)瓦納古陸解體時(shi)，印(yin)(yin)(yin)(yin)(yin)(yin)度(du)、澳(ao)大(da)利(li)亞(ya)(ya)大(da)陸、南(nan)(nan)(nan)極(ji)大(da)陸、非(fei)洲大(da)陸和(he)(he)南(nan)(nan)(nan)美大(da)陸的(de)(de)(de)漂移而形成的(de)(de)(de)。
