1 Beneath the palisade layer is the spongy layer. 2  The cells of the spongy layer are more branched and not so tightly packed, so that there are large intercellular air spaces between them for oxygen and carbon dioxide to diffuse in and out of during respiration and photosynthesis. leaf is an organ of a vascular plant and is the principal lateral appendage of the stem. The leaves and stem together form the shoot. Foliage is a mass noun that refers to leaves collectively. Typically a leaf is a thin, dorsiventrally flattened organ, borne above ground and specialized for photosynthesis.
A rift valley is a lowland region formed by the interaction of Earth's tectonic plates. This small rift valley has a typical formationâlong, narrow, and deep. It was formed by the Thingvellir rift, where the North American and Eurasian tectonic plates are tearing, or rifting, apart over a hotspot on the island of Iceland.
Rift valleys can be very deep, and both such valleys known to exist in continental areas on Earth, the East African Rift and the Siberian Baikal Rift, have large, deep lakes in them. As the walls of a rift valley are pulled apart, the floor of the valley tends to sink. If this subsidence happens faster than erosion from the walls can fill it in with sediment, the floor of the valley continues to fall relative to the surrounding terrain.