[1] myr - Wikipedia () https://en.wikipedia.org/wiki/Myr
[2] Date and Time Formats - CollectiveAccess Documentation () https://docs.collectiveaccess.org/wiki/Date_and_Time_Formats
[3] Year - Wikipedia () https://en.wikipedia.org/wiki/Year#Mya
[4] 年 - Wikipedia, , https://ja.wikipedia.org/wiki/%E5%B9%B4#%E6%B4%BE%E7%94%9F%E5%8D%98%E4%BD%8D
[5] 氷河時代の年表 - Wikipedia, , https://ja.wikipedia.org/wiki/%E6%B0%B7%E6%B2%B3%E6%99%82%E4%BB%A3%E3%81%AE%E5%B9%B4%E8%A1%A8
最も厳しかったとされる2番目の氷河時代は720–635 Ma (百万年) 前[2]の新原生代に起きたと推定されており、
一連の小規模な氷期は460 Maから430 Maの間に起きた。さらに、350 Maから250 Maの間にも大規模な氷河時代があった。
年代 (ka)
Surface and near surface rocks of Ethiopia are comprised of the three rock types, and in general each rock type was formed over a specific span of time that is measured in millions of years (Ma).
1. Precambrian (before 570 Ma). Metamorphic rocks of great antiquity are currently exposed in the southwest in Wellega and Illubabor, in the South in Sidamo, in the southeast in Harrarghe, in the northwest and north in Eritrea and Tigre.