The following text is for questions 6 to 10.

Permafrost is any ground that remains completely frozen32F (0C) or colderfor at least two years straight. These permanently frozen grounds are most common in regions with high mountains and in Earth's higher latitudesnear the North and South Poles. Permafrost covers large regions of the Earth. Almost a quarter of the land area in the Northern Hemisphere has permafrost underneath. Although the ground is frozen, permafrost regions are not always covered in snow.

Permafrost is made of a combination of soil, rocks and sand that are held together by ice. The soil and ice in permafrost stay frozen all year long. Near the surface, permafrost soils also contain large quantities of organic carbona material leftover from dead plants that couldn't decompose, or rot away, due to the cold. Lower permafrost layers contain soils made mostly of minerals.

A layer of soil on top of permafrost does not stay frozen all year. This layer, called the active layer, thaws during the warm summer months and freezes again in the fall. In colder regions, the ground rarely thawseven in the summer. There, the active layer is very thinonly 4 to 6 inches (10 to 15 centimeters). In warmer permafrost regions, the active layer can be several meters thick.

(Adapted from https://climatekids.nasa.gov/menu/weather-and-climate/)

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