C Finn
Painted Hills
Formation
The Painted Hills began to form 35 million years ago when pumice and ash from volcanic eruptions in the Cascade Mountains traveled 100 miles east and settled over the area. Once there, the ash and other sediments were mixed by natural processes including the flow of water, growth of plants, and the movement of animals. Over time, this led to oxidation of the ash on the surface. Buried under new layers and deposits, the ash turned into soils by way of compaction and cementation. With more time and weathering, the exterior surfaces of The Painted Hills were worn into clay. Now, they are primarily made of hard claystone layers.
Layers
The colored bands are due to changes in climate that occurred as they were distributed through time. As the climate changed to a more tropical setting with distinct wet and dry seasons, reddish and yellowish layers formed that are made up of laterites, soils rich in iron and aluminum. Red soils come from a more tropical period, while the yellows are from a drier and cooler time. The red coloring is laterite soil that formed by floodplain deposits when the area was warm and humid. The darker, black soil is lignite that was vegetative matter that grew along the floodplain. The grey coloring is mudstone, siltstone, and shale.
An abundance of fossil remains of early horses, camels, and rhinoceroses in the Painted Hills unit makes the area particularly important to vertebrate paleontologists.
Painted Hills
Formation
The Painted Hills began to form 35 million years ago when pumice and ash from volcanic eruptions in the Cascade Mountains traveled 100 miles east and settled over the area. Once there, the ash and other sediments were mixed by natural processes including the flow of water, growth of plants, and the movement of animals. Over time, this led to oxidation of the ash on the surface. Buried under new layers and deposits, the ash turned into soils by way of compaction and cementation. With more time and weathering, the exterior surfaces of The Painted Hills were worn into clay. Now, they are primarily made of hard claystone layers.
Layers
The colored bands are due to changes in climate that occurred as they were distributed through time. As the climate changed to a more tropical setting with distinct wet and dry seasons, reddish and yellowish layers formed that are made up of laterites, soils rich in iron and aluminum. Red soils come from a more tropical period, while the yellows are from a drier and cooler time. The red coloring is laterite soil that formed by floodplain deposits when the area was warm and humid. The darker, black soil is lignite that was vegetative matter that grew along the floodplain. The grey coloring is mudstone, siltstone, and shale.
An abundance of fossil remains of early horses, camels, and rhinoceroses in the Painted Hills unit makes the area particularly important to vertebrate paleontologists.