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.
As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior (the asthenosphere). The sinking of the block forms a central valley called a rift. Magma (liquid rock) seeps upward to fill the cracks. In this way, new crust is formed along the boundary.Earthquakes occur along the faults, and volcanoes form where the magma reaches the surface. Where a divergent boundary crosses the land, the rift valleys which form are typically 30 to 50 kilometers wide.Examples include th e East Africa rift in Kenya and Ethiopia, and the Rio Grande rift in New Mexico.here a divergent boundary crosses the land, the rift valleys which form are typically 30 to 50 kilometers wide. Examples include th e East Africa rift in Kenya and Ethiopia, and the Rio Grande rift in New Mexico.