ParsonParkB

Parsons Park

Ethalyn Thomas Park

Although surrounded by streets, this little island has several interesting natural features and is well worth crossing the street from Parsons Park.

	Redwoods (Sequoia sempervirens). Most of the trees in this small park are coast redwoods. These are native California trees. They can grow to be 200–300 feet tall and more, and they grow quite fast: up to 60 feet in only 20 years. Redwoods are conical in shape with horizontal or slightly drooping branches. The roots are wide spread but shallow. The flat leaves are 15–25 mm long and flat, and the cones are 15–32 mm long. Redwoods reproduce through seeds or by sprouting from the root crown, stump, or a fallen branch. Often a ring of redwoods will indicate where a “mother” tree once was. And a straight line of trees will result from a fallen tree. In Parsons Park, several of the redwoods have sprouts growing at their base.
	Cork oak. The Cork Oak (Quercus suber) is originally from southwest Europe and northwest Africa. This evergreen oak grows to heights of about 60 feet with leaves that are 1-2 inches long, The acorns are about an inch long. The hallmark of the cork oak is its thick, rugged bark. Every 10-12 years, this beautiful bark is harvested to make corks. This process does not hurt the tree at all, and the trees sometimes live for 250 years.
	Basalt is rich in magnesium and iron and poor in aluminum and silica. It forms very dark, heavy volcanic rock with fine grains due to its relatively rapid cooling. Over time, the color weathers to become brown or even reddish.
	Andesite is an intermediate form with much less silica and aluminum and more iron and magnesium. It forms gray to black volcanic rock that usually contains visible crystals.
	Sandstone. Much of Castro Valley stands on sandstone, and outcrops of it can be found throughout the area. Since most sand is made of quartz, sandstone is mostly quartz. Other “impurities,” such as clay, hematite, ilmenite, feldspar, and mica, add color to the sandstone. Iron compounds can make sandstone tan or brown. Sandstones with more impurities are called wacke or graywacke. Sandstone is a sedimentary rock formed from (not surprisingly) grains of sand (0.0625 to 2 mm in size). For example, over time, the sand in an old river delta or ancient beach becomes stuck together by much finer particles of quartz, calcium carbonate or iron oxide, sometimes produced from volcanic ash. An outcrop of sandstone can tell us a lot about geologic history, but typically few fossils are found in sandstone.