Martinez

Deep time

The ground under you was mud, settled under water.

The rock here is mapped as siltstone, sandstone and shale, from 252 to 66 million years ago, the age of dinosaurs.

Rock like this forms from fine mud settling in still water, a sea or a lake, and pressing into stone.

On top of it lies Cut and fill land-Diablo complex, a soil that takes in rain slowest of all and sheds most of it.

Sources: Macrostrat geologic map The map it was compiled from USDA soil survey, via SoilWeb

Every rain

A stream or river lies 0.4 miles southwest of the pin.

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Sources: US Fish and Wildlife Service wetlands map

Before settlement

This ground was open grassland, and fire came every 4 years.

LANDFIRE's model of this ground before European settlement: 77% of it within half a mile was California Central Valley and Southern Coastal Grassland, with California Central Valley Mixed Oak Savanna on 10%.

Sources: LANDFIRE Biophysical Settings

Since 1897

Roofs and roads came. The ground still moves.

USGS first mapped this spot in 1897.

Today the ground within half a mile is 39% roads and 38% buildings and pavement.

14 old landslides are mapped in the slopes within half a mile.

The record flood at the nearest gauge, Walnut Creek at Concord, came on 5 January 1982.

Sources: USGS first map, 1897 (PDF) All the USGS maps here, on topoView LANDFIRE Existing Vegetation Type USGS landslide inventory USGS gauge: Walnut Creek at Concord