"Permafrost" Natural Recordings by Native Speakers
Permafrost refers to a type of soil or rock that remains frozen for two or more consecutive years. It is commonly found in Arctic and sub-Arctic regions, where temperatures are typically below freezing for long periods of time. Permafrost can be hundreds or even thousands of years old and can be several meters thick. It is formed when the ground remains frozen for a long time, causing the soil and underlying rock to become compact and rigid. Permafrost plays an important role in the ecosystem, providing habitat for certain plants and animals that are adapted to the frozen conditions.
Perlite is a type of volcanic glass that is used as a lightweight aggregate in construction materials, such as building insulation, and also as a soil amendment in horticulture. It is created when obsidian lava is rapidly cooled, which causes it to expand like popcorn and form a lightweight, porous, and inert material. Perlite is often used to improve soil drainage and aeration, increase water retention, and reduce soil compaction. It is also used as a substrate in hydroponic systems and as an additive in some types of concrete.