What term refers to an outer enclosure that offers protection from the earth load while also possessing sealing qualities?

The term that best describes an outer enclosure providing protection from the earth load while also having sealing qualities is "vault." A vault is typically constructed as a secure and enclosed structure, often used in contexts such as burial or storage, where it must withstand the weight of the earth above it and protect the contents from external elements. The sealing characteristics of a vault make it an excellent choice for preservation, ensuring that what is enclosed remains protected from moisture and other environmental factors. This is essential in applications like burial practices, where maintaining the integrity of the remains or artifacts inside is of utmost importance.

On the other hand, while a casket is designed to hold remains, it does not necessarily provide the same level of environmental sealing or structural integrity against earth loads as a vault does. A crypt is an above-ground tomb that can resemble a vault but may not provide the same comprehensive protective qualities. A tombstone primarily serves as a marker for graves and does not function as an enclosure meant to offer protection from loads or sealing qualities. Thus, the features and purpose of a vault align perfectly with the question’s requirements.