*5.4. Hurricane Frequency*

As many as 25 to 30 tropical depressions originate each year near Acapulco off western Mexico between the months of May and November before intensifying in strength and shifting northwest into the eastern Pacific Ocean [22]. Especially during El Niño events every 6 to 8 years, a few storms turn northward into the Gulf of California. In recent years, several hurricanes have struck the southern tip of the Baja California peninsula and followed tracks crossing Isla Cerralvo in the southern gulf region, where heavy rainfall flushes arroyo sediments to form tide-water deltas at some 39 localities around the island's circumference [23]. Long-shore currents stimulated by the winter winds also play a role in truncating those deltas and sending the sediment load south along both sides of the island. Hurricanes that manage

to enter the gulf usually lose energy rapidly before continuing as downgraded storms, although Hurricane Odile is a recent exception, reaching Loreto at hurricane strength in 2014. The driest part of the Baja California peninsula is located far to the north in the upper Gulf of California, where normal rainfall amounts to only 5 cm per year. A remnant of Hurricane Odile was the last big storm to bring excess water to the area. In particular, the large Costilla Delta that empties sediments from Heme Canyon south of Puertecitos (Figure 1a) lends evidence to the effect of episodic rain storms that flush the region, although a nearby salt lagoon also attests to long periods of aridity [24]. The bar that closes off the salt lagoon was constructed under the influence of long-shore currents based on the occurrence of pumice cobbles derived from strata within Heme Canyon and transferred seaward via the Costilla Delta.

Although clearly episodic in frequency and less common in the northern Gulf of California, hurricanes are the major factor capable of expending su fficient energy to shape the landscapes of peninsular Baja California through the agencies of stream erosion and shore modification. The Almeja CBB, in particular, stands out as a prime example of a large but distinctly asymmetrical deposit that only could have been formed under the influence of incremental additions due to Holocene hurricanes with a counter-clockwise rotation sending wave surge westward across the headland.

## *5.5. Human Occupation of the San Basilio Area*

Archeological evidence of kitchen middens including worked flakes of obsidian occurs on the northwest shore of Ensenada San Basilio in one of the most sheltered corners of the bay. Cave paintings also are known from a locality on the south side of the bay. These remains indicate that the area has a history of occupation predating the arrival of Europeans. No trace of habitation is known from nearby Ensenada Almeja, possibly because of exposure to the seasonal north winds. Nonetheless, native peoples would have been subjected to storm conditions from time to time.
