印度洋(yang)在古代(dai)稱為“厄立(li)特(te)里亞(ya)海(hai)”，早見于古希(xi)臘地(di)理學(xue)家希(xi)羅多德（前484-前425年）所(suo)著《歷史》一書及其編繪的(de)世界地(di)圖中。“厄里特(te)里亞(ya)”（ERYTHREA）希(xi)臘文原(yuan)意為紅(hong)色，全名意為紅(hong)海(hai)。
“印度洋”這(zhe)一(yi)名(ming)稱(cheng)相對出現(xian)得較(jiao)晚。公(gong)元1世紀后(hou)期的羅(luo)馬地理(li)學家彭波尼烏斯(si)·梅拉(la)可能是早使用此名(ming)的人。公(gong)元10世紀，阿拉(la)伯(bo)人伊本·豪卡勒編繪的世界地圖上也(ye)使用了這(zhe)個(ge)名(ming)字。
近代正(zheng)式使用印(yin)度洋(yang)一名則是(shi)在1515年(nian)左右，當時中(zhong)歐(ou)地(di)圖(tu)學家舍納(na)爾編繪的地(di)圖(tu)上，把這片大洋(yang)標注為“東(dong)方的印(yin)度洋(yang)”，此處的“東(dong)方”一詞是(shi)與大西洋(yang)相對而(er)言(yan)的。
1497年(nian)，葡萄牙航海(hai)家達(da)·伽(jia)馬東航尋找(zhao)印度，便將沿途所經過的洋面統稱之為印度洋。
1570年奧(ao)爾太利烏斯(si)編繪(hui)的(de)(de)世界地(di)圖(tu)集中，把“東方(fang)的(de)(de)印(yin)度洋(yang)”一(yi)名去掉“東方(fang)的(de)(de)”，簡(jian)化(hua)為“印(yin)度洋(yang)”。這個(ge)名字(zi)逐漸被(bei)人們接受，成為通用的(de)(de)稱(cheng)呼。
印度洋是聯系亞洲(zhou)(zhou)、非洲(zhou)(zhou)和(he)大洋洲(zhou)(zhou)之(zhi)間的(de)交通要(yao)道(dao)。從印度洋往西(xi)北通過(guo)曼德海(hai)(hai)峽、紅海(hai)(hai)；蘇(su)伊士運河、地中(zhong)海(hai)(hai)和(he)直布羅陀海(hai)(hai)峽到達西(xi)歐；向西(xi)南經(jing)好望角進入(ru)大西(xi)洋，通向歐美沿(yan)海(hai)(hai)各(ge)地；向東北經(jing)馬(ma)六甲海(hai)(hai)峽和(he)龍(long)目(mu)海(hai)(hai)峽進入(ru)太平洋。印度洋沿(yan)岸是世界資(zi)源的(de)一個重要(yao)出口(kou)地，沿(yan)岸各(ge)國出口(kou)的(de)石油、礦砂、橡膠(jiao)、棉花、糧食和(he)進口(kou)的(de)水泥、機械產品(pin)(pin)和(he)化工產品(pin)(pin)等大宗貨(huo)物都(dou)需要(yao)依靠廉價(jia)的(de)海(hai)(hai)洋運輸(shu)，再(zai)加上大量(liang)的(de)過(guo)境運輸(shu)，使(shi)印度洋有較(jiao)大的(de)運輸(shu)量(liang)，擁有世界l/6的(de)貨(huo)物吞吐量(liang)和(he)近1/10的(de)貨(huo)物周轉量(liang)。
印(yin)(yin)度洋(yang)(yang)的航(hang)(hang)(hang)運(yun)(yun)業雖不如大西(xi)洋(yang)(yang)和太平洋(yang)(yang)發達，但由于中東(dong)(dong)(dong)(dong)地區盛產的石油(you)(you)通過(guo)印(yin)(yin)度洋(yang)(yang)航(hang)(hang)(hang)線源源不斷向外輸(shu)出(chu)，因而(er)(er)印(yin)(yin)度洋(yang)(yang)航(hang)(hang)(hang)線在世界(jie)上(shang)(shang)占有(you)重(zhong)要的地位。印(yin)(yin)度洋(yang)(yang)上(shang)(shang)運(yun)(yun)輸(shu)石油(you)(you)的航(hang)(hang)(hang)線有(you)兩條：一條是出(chu)波斯灣向西(xi)，繞過(guo)南非的好望角或(huo)者通過(guo)紅海(hai)、蘇伊士運(yun)(yun)河(he)，到(dao)歐洲和美國。這(zhe)是世界(jie)上(shang)(shang)重(zhong)要的石油(you)(you)運(yun)(yun)輸(shu)線。一條是出(chu)波斯灣向東(dong)(dong)(dong)(dong)，穿過(guo)馬六甲(jia)海(hai)峽或(huo)龍目海(hai)峽到(dao)日本(ben)和東(dong)(dong)(dong)(dong)亞其(qi)他國家。霍(huo)(huo)爾(er)木(mu)茲海(hai)峽在印(yin)(yin)度洋(yang)(yang)航(hang)(hang)(hang)線上(shang)(shang)占有(you)重(zhong)要地位，波斯灣地區出(chu)口石油(you)(you)總(zong)量(liang)90%從此海(hai)峽運(yun)(yun)出(chu)，因而(er)(er)霍(huo)(huo)爾(er)木(mu)茲海(hai)峽被稱為“石油(you)(you)海(hai)峽”。蘇伊士運(yun)(yun)河(he)經(jing)(jing)馬六甲(jia)海(hai)峽的航(hang)(hang)(hang)線，是印(yin)(yin)度洋(yang)(yang)東(dong)(dong)(dong)(dong)西(xi)間一條重(zhong)要的航(hang)(hang)(hang)道，運(yun)(yun)輸(shu)量(liang)巨(ju)大，它將西(xi)歐、地中海(hai)沿岸各國的經(jing)(jing)濟(ji)與遠東(dong)(dong)(dong)(dong)及北美洲西(xi)海(hai)岸各國的經(jing)(jing)濟(ji)緊密(mi)地聯系起來。
印度洋(yang)(yang)的(de)(de)地理位置非(fei)常(chang)重要(yao)，是溝(gou)通(tong)(tong)亞(ya)(ya)洲(zhou)、非(fei)洲(zhou)、歐洲(zhou)和大洋(yang)(yang)洲(zhou)的(de)(de)交(jiao)通(tong)(tong)要(yao)道(dao)。向(xiang)(xiang)東(dong)通(tong)(tong)過馬六甲海(hai)(hai)峽可以(yi)進入(ru)太平洋(yang)(yang)，向(xiang)(xiang)西(xi)繞過好望角可達大西(xi)洋(yang)(yang)，向(xiang)(xiang)西(xi)北(bei)通(tong)(tong)過紅海(hai)(hai)、蘇伊士運河，可入(ru)地中海(hai)(hai)。航(hang)線(xian)(xian)主要(yao)由亞(ya)(ya)、歐航(hang)線(xian)(xian)和南(nan)亞(ya)(ya)、東(dong)南(nan)亞(ya)(ya)、南(nan)非(fei)、大洋(yang)(yang)洲(zhou)之間的(de)(de)航(hang)線(xian)(xian)。印度洋(yang)(yang)的(de)(de)海(hai)(hai)底電纜(lan)多分布在北(bei)部，重要(yao)的(de)(de)線(xian)(xian)路有亞(ya)(ya)丁(ding)—孟買—馬德拉斯(si)—新(xin)加坡(po)線(xian)(xian)；亞(ya)(ya)丁(ding)—科(ke)(ke)倫坡(po)線(xian)(xian)；東(dong)非(fei)沿(yan)岸線(xian)(xian)。塞舌爾群島(dao)的(de)(de)馬埃島(dao)、毛里(li)求斯(si)島(dao)和科(ke)(ke)科(ke)(ke)斯(si)群島(dao)是主要(yao)的(de)(de)海(hai)(hai)底電纜(lan)樞(shu)紐(niu)站。沿(yan)岸港口終(zhong)年不凍，四(si)季通(tong)(tong)航(hang)。
印度洋(yang)(yang)西南(nan)(nan)以通(tong)過(guo)南(nan)(nan)非厄加(jia)勒斯(si)特的(de)經線(xian)同大西洋(yang)(yang)分界(jie)，東南(nan)(nan)以通(tong)過(guo)塔斯(si)馬尼(ni)亞島東南(nan)(nan)角至南(nan)(nan)極大陸的(de)經線(xian)與(yu)太平洋(yang)(yang)聯(lian)結。印度洋(yang)(yang)的(de)輪廓(kuo)為(wei)北(bei)部(bu)為(wei)陸地(di)封閉(bi)，南(nan)(nan)面則以南(nan)(nan)緯60°為(wei)界(jie)，與(yu)南(nan)(nan)冰洋(yang)(yang)相連。
印(yin)度洋的主要屬海(hai)和海(hai)灣(wan)(wan)是紅海(hai)、阿拉伯海(hai)、亞(ya)(ya)丁灣(wan)(wan)、波斯灣(wan)(wan)、阿曼灣(wan)(wan)、孟加拉灣(wan)(wan)、安(an)達曼海(hai)、阿拉弗拉海(hai)、帝(di)汶(wen)海(hai)、卡奔(ben)塔利亞(ya)(ya)灣(wan)(wan)、大澳大利亞(ya)(ya)灣(wan)(wan)、莫桑比克海(hai)峽等(deng)等(deng)。
印(yin)度洋有(you)很多島(dao)(dao)(dao)嶼，其(qi)中大(da)(da)部(bu)分(fen)是(shi)大(da)(da)陸島(dao)(dao)(dao)，如(ru)馬(ma)達(da)加(jia)(jia)斯加(jia)(jia)島(dao)(dao)(dao)、斯里蘭卡島(dao)(dao)(dao)、安達(da)曼群(qun)(qun)島(dao)(dao)(dao)、尼科(ke)巴群(qun)(qun)島(dao)(dao)(dao)、明打威群(qun)(qun)島(dao)(dao)(dao)等。留(liu)尼汪島(dao)(dao)(dao)、科(ke)摩羅群(qun)(qun)島(dao)(dao)(dao)、阿姆斯特(te)丹島(dao)(dao)(dao)、克羅澤群(qun)(qun)島(dao)(dao)(dao)、凱爾蓋(gai)朗群(qun)(qun)島(dao)(dao)(dao)為火山島(dao)(dao)(dao)。拉克沙(sha)群(qun)(qun)島(dao)(dao)(dao)、馬(ma)爾代夫群(qun)(qun)島(dao)(dao)(dao)、查戈(ge)斯群(qun)(qun)島(dao)(dao)(dao)，以及爪哇西南(nan)的(de)圣誕島(dao)(dao)(dao)、科(ke)科(ke)斯群(qun)(qun)島(dao)(dao)(dao)都是(shi)珊瑚島(dao)(dao)(dao)，馬(ma)達(da)加(jia)(jia)斯加(jia)(jia)島(dao)(dao)(dao)是(shi)南(nan)回歸線穿(chuan)過(guo)的(de)島(dao)(dao)(dao)。
印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)底(di)地貌錯(cuo)綜復(fu)雜，除洋(yang)(yang)(yang)(yang)(yang)(yang)底(di)中(zhong)(zhong)部(bu)(bu)有(you)呈“入(ru)”字形(xing)的(de)大(da)洋(yang)(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)脊(ji)外，東(dong)部(bu)(bu)尚有(you)東(dong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)和(he)島(dao)弧、海(hai)(hai)(hai)(hai)(hai)(hai)溝帶(dai)(dai)(dai)，在海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)、海(hai)(hai)(hai)(hai)(hai)(hai)丘(qiu)、海(hai)(hai)(hai)(hai)(hai)(hai)臺之間分布著(zhu)許多海(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)。印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)的(de)大(da)洋(yang)(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)脊(ji)，包括中(zhong)(zhong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)、阿拉伯一(yi)(yi)印(yin)(yin)度(du)(du)(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)、西(xi)(xi)南(nan)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)和(he)東(dong)南(nan)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)。中(zhong)(zhong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)°嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)從(cong)阿姆斯(si)(si)特(te)(te)丹島(dao)向(xiang)北延(yan)伸，一(yi)(yi)般(ban)高(gao)于兩側(ce)海(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)(pen)1300-2500米(mi)，平均寬度(du)(du)(du)(du)(du)達800千(qian)(qian)米(mi)左右，由(you)于被(bei)一(yi)(yi)些(xie)(xie)與(yu)之垂直或(huo)斜(xie)交(jiao)的(de)斷(duan)裂帶(dai)(dai)(dai)切斷(duan)錯(cuo)開(kai)，中(zhong)(zhong)脊(ji)裂谷表現時(shi)斷(duan)時(shi)續(xu)(xu)的(de)特(te)(te)征，因(yin)此中(zhong)(zhong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)形(xing)態崎嶇破碎。中(zhong)(zhong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)向(xiang)西(xi)(xi)北延(yan)伸形(xing)成阿拉伯一(yi)(yi)印(yin)(yin)度(du)(du)(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)，高(gao)度(du)(du)(du)(du)(du)較大(da)，繼續(xu)(xu)向(xiang)西(xi)(xi)北延(yan)伸，進入(ru)亞丁灣和(he)紅海(hai)(hai)(hai)(hai)(hai)(hai)；中(zhong)(zhong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)從(cong)羅德里格(ge)斯(si)(si)島(dao)向(xiang)西(xi)(xi)南(nan)分出西(xi)(xi)南(nan)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)，經愛德華太子群(qun)島(dao)，接(jie)大(da)西(xi)(xi)洋(yang)(yang)(yang)(yang)(yang)(yang)一(yi)(yi)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)；中(zhong)(zhong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)至(zhi)圣波爾島(dao)向(xiang)東(dong)南(nan)連接(jie)東(dong)南(nan)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)，再向(xiang)東(dong)連接(jie)太平洋(yang)(yang)(yang)(yang)(yang)(yang)一(yi)(yi)南(nan)極海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)和(he)東(dong)太平洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)。印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)底(di)除中(zhong)(zhong)脊(ji)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)外，還有(you)許多近似南(nan)北向(xiang)的(de)構造帶(dai)(dai)(dai)。這(zhe)些(xie)(xie)構造帶(dai)(dai)(dai)相互(hu)平行，綿延(yan)很遠(yuan)，其中(zhong)(zhong)東(dong)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)，走向(xiang)與(yu)東(dong)經90°經線一(yi)(yi)致，是世界上較直的(de)一(yi)(yi)條(tiao)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)。它北起北緯10°附近的(de)安達曼群(qun)島(dao)，南(nan)至(zhi)南(nan)緯3l° 的(de)斷(duan)裂海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)，長約5 000千(qian)(qian)米(mi)，東(dong)西(xi)(xi)寬約150-250千(qian)(qian)米(mi)。由(you)于它沿著(zhu)東(dong)經90°分布，故又叫東(dong)經90° 海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)或(huo)卡彭特(te)(te)海(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)(ling)。大(da)洋(yang)(yang)(yang)(yang)(yang)(yang)中(zhong)(zhong)脊(ji)呈“入(ru)”字形(xing)，將(jiang)印(yin)(yin)度(du)(du)(du)(du)(du)洋(yang)(yang)(yang)(yang)(yang)(yang)分成三個海(hai)(hai)(hai)(hai)(hai)(hai)域。
印度(du)洋屬海(hai)(hai)(hai)(hai)較(jiao)(jiao)少。內(nei)海(hai)(hai)(hai)(hai)有(you)(you)紅海(hai)(hai)(hai)(hai)和(he)波(bo)斯(si)(si)灣(wan)；邊緣海(hai)(hai)(hai)(hai)有(you)(you)西北(bei)(bei)部(bu)(bu)的(de)(de)(de)阿(a)拉伯(bo)海(hai)(hai)(hai)(hai)，東(dong)北(bei)(bei)部(bu)(bu)的(de)(de)(de)安達曼(man)海(hai)(hai)(hai)(hai)，東(dong)部(bu)(bu)的(de)(de)(de)帝(di)汶海(hai)(hai)(hai)(hai)和(he)阿(a)拉弗(fu)拉海(hai)(hai)(hai)(hai)；大(da)(da)(da)海(hai)(hai)(hai)(hai)灣(wan)有(you)(you)西北(bei)(bei)部(bu)(bu)的(de)(de)(de)亞(ya)丁(ding)灣(wan)和(he)阿(a)曼(man)灣(wan)，東(dong)北(bei)(bei)部(bu)(bu)的(de)(de)(de)孟加(jia)拉灣(wan)，澳(ao)(ao)大(da)(da)(da)利(li)(li)(li)(li)亞(ya)北(bei)(bei)面(mian)的(de)(de)(de)卡(ka)奔塔利(li)(li)(li)(li)亞(ya)灣(wan)（Carpentaria）、南面(mian)的(de)(de)(de)大(da)(da)(da)澳(ao)(ao)大(da)(da)(da)利(li)(li)(li)(li)亞(ya)灣(wan)。在(zai)南極洲(zhou)海(hai)(hai)(hai)(hai)域(yu)也有(you)(you)一(yi)些屬海(hai)(hai)(hai)(hai)。海(hai)(hai)(hai)(hai)岸線除北(bei)(bei)部(bu)(bu)比(bi)(bi)較(jiao)(jiao)曲折(zhe)之外，大(da)(da)(da)部(bu)(bu)分平(ping)直，少島(dao)(dao)(dao)嶼。大(da)(da)(da)島(dao)(dao)(dao)有(you)(you)馬(ma)達加(jia)斯(si)(si)加(jia)島(dao)(dao)(dao)、索科特拉（Socotra）島(dao)(dao)(dao)、斯(si)(si)里蘭卡(ka)島(dao)(dao)(dao)，還有(you)(you)塞席爾群(qun)島(dao)(dao)(dao)；火山島(dao)(dao)(dao)有(you)(you)科摩羅（Comoros）群(qun)島(dao)(dao)(dao)、馬(ma)斯(si)(si)克林（Mascarene）群(qun)島(dao)(dao)(dao)和(he)凱(kai)爾蓋朗(lang)（Kerguelen）群(qun)島(dao)(dao)(dao)；珊瑚島(dao)(dao)(dao)有(you)(you)馬(ma)爾代(dai)夫(fu)群(qun)島(dao)(dao)(dao)。大(da)(da)(da)陸(lu)(lu)(lu)邊緣地帶包(bao)括大(da)(da)(da)陸(lu)(lu)(lu)棚和(he)大(da)(da)(da)陸(lu)(lu)(lu)坡(po)。大(da)(da)(da)陸(lu)(lu)(lu)棚一(yi)般(ban)比(bi)(bi)較(jiao)(jiao)狹窄，大(da)(da)(da)陸(lu)(lu)(lu)棚較(jiao)(jiao)寬(kuan)的(de)(de)(de)海(hai)(hai)(hai)(hai)域(yu)有(you)(you)阿(a)拉伯(bo)海(hai)(hai)(hai)(hai)、安達曼(man)海(hai)(hai)(hai)(hai)、孟加(jia)拉灣(wan)和(he)大(da)(da)(da)澳(ao)(ao)大(da)(da)(da)利(li)(li)(li)(li)亞(ya)灣(wan)，寬(kuan)處在(zai)澳(ao)(ao)大(da)(da)(da)利(li)(li)(li)(li)亞(ya)至新(xin)幾內(nei)亞(ya)島(dao)(dao)(dao)之間，約965千米。大(da)(da)(da)陸(lu)(lu)(lu)坡(po)陡峻之處坡(po)度(du)10°-30°，一(yi)般(ban)坡(po)度(du)較(jiao)(jiao)小(xiao)。在(zai)印度(du)河(he)、恒河(he)入海(hai)(hai)(hai)(hai)口外的(de)(de)(de)海(hai)(hai)(hai)(hai)域(yu)，有(you)(you)面(mian)積(ji)寬(kuan)廣的(de)(de)(de)水下(xia)沖積(ji)扇，被水下(xia)峽谷所(suo)切割。
島(dao)(dao)弧(hu)帶(dai)(dai)從(cong)緬甸(dian)至(zhi)澳大(da)(da)(da)利(li)(li)亞延伸達5150千(qian)米，可分為(wei)(wei)兩列(lie)平(ping)行的島(dao)(dao)鏈：內弧(hu)屬火山島(dao)(dao)，有(you)(you)大(da)(da)(da)、小(xiao)巽他群(qun)島(dao)(dao)（包(bao)括(kuo)蘇門(men)答臘島(dao)(dao)、爪哇島(dao)(dao)、帝汶(wen)島(dao)(dao)等(deng)）；外(wai)弧(hu)為(wei)(wei)非(fei)(fei)火山島(dao)(dao)，有(you)(you)安達曼群(qun)島(dao)(dao)、尼科(ke)巴(ba)（Nicobar）群(qun)島(dao)(dao)、明打(da)威（Mentawai）群(qun)島(dao)(dao)等(deng)。島(dao)(dao)弧(hu)的外(wai)緣——爪哇海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)溝為(wei)(wei)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋水域，深(shen)點7450米。印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋中(zhong)央的海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)可分為(wei)(wei)3支(zhi)：北支(zhi)為(wei)(wei)阿(a)拉(la)伯——印(yin)(yin)(yin)度(du)(du)(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)；西(xi)南(nan)(nan)(nan)(nan)支(zhi)為(wei)(wei)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋西(xi)南(nan)(nan)(nan)(nan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)，它與(yu)大(da)(da)(da)西(xi)洋——印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)相(xiang)連；東(dong)(dong)南(nan)(nan)(nan)(nan)支(zhi)為(wei)(wei)中(zhong)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)，它與(yu)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋東(dong)(dong)南(nan)(nan)(nan)(nan)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)相(xiang)接。北支(zhi)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)和西(xi)南(nan)(nan)(nan)(nan)支(zhi)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)是結構復雜的海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)底山脈(mo)，寬(kuan)度(du)(du)(du)(du)(du)400-970千(qian)米，相(xiang)對高度(du)(du)(du)(du)(du)1830-3050米，海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)的中(zhong)脊為(wei)(wei)裂(lie)谷(gu)帶(dai)(dai)，地貌極為(wei)(wei)崎嶇險(xian)峻；東(dong)(dong)南(nan)(nan)(nan)(nan)支(zhi)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)從(cong)中(zhong)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)至(zhi)阿(a)姆斯(si)特(te)丹島(dao)(dao)的寬(kuan)度(du)(du)(du)(du)(du)達1450千(qian)米，裂(lie)谷(gu)很少(shao)。印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋中(zhong)央的海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)被大(da)(da)(da)小(xiao)不(bu)一(yi)的斷(duan)裂(lie)帶(dai)(dai)所切割，例如歐文(wen)斷(duan)裂(lie)帶(dai)(dai)，即(ji)延伸至(zhi)阿(a)拉(la)伯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)和索(suo)馬利(li)(li)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)，海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)底巖層位(wei)移達320千(qian)米。印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋東(dong)(dong)部(bu)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)域1962年發(fa)現的東(dong)(dong)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)（或稱(cheng)「東(dong)(dong)經九十度(du)(du)(du)(du)(du)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)」），南(nan)(nan)(nan)(nan)北直線延伸約4990千(qian)米，為(wei)(wei)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋中(zhong)較(jiao)長較(jiao)直的海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)。海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)嶺(ling)(ling)(ling)之間為(wei)(wei)一(yi)系列(lie)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)︰北部(bu)和西(xi)北部(bu)有(you)(you)阿(a)拉(la)伯海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)、索(suo)馬利(li)(li)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)；中(zhong)部(bu)自西(xi)而東(dong)(dong)，有(you)(you)馬達加(jia)斯(si)加(jia)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)、中(zhong)印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)、科(ke)科(ke)斯(si)海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)和北澳大(da)(da)(da)利(li)(li)亞海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)；南(nan)(nan)(nan)(nan)部(bu)重要的是克羅澤（Crozet）海(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)(hai)盆(pen)。根據大(da)(da)(da)陸(lu)(lu)漂移學說，印(yin)(yin)(yin)度(du)(du)(du)(du)(du)洋是在中(zhong)生代（距今6500萬-22500萬年前）南(nan)(nan)(nan)(nan)半球貢德瓦納古(gu)陸(lu)(lu)解體時，印(yin)(yin)(yin)度(du)(du)(du)(du)(du)、澳大(da)(da)(da)利(li)(li)亞大(da)(da)(da)陸(lu)(lu)、南(nan)(nan)(nan)(nan)極大(da)(da)(da)陸(lu)(lu)、非(fei)(fei)洲大(da)(da)(da)陸(lu)(lu)和南(nan)(nan)(nan)(nan)美大(da)(da)(da)陸(lu)(lu)的漂移而形成的。
