strontium 90: a radioactive isotope of strontium (with the mass number 90) that is present in the fallout from nuclear explosions; can be assimilated like calcium into bones
strontium: a soft silver-white or yellowish metallic element of the alkali metal group; turns yellow in air; occurs in celestite and strontianite
giant tortoise: very large tortoises of the Galapagos and Seychelles islands