denote an annual average from . It has hot dry summers, as does all of Adelaide, and December to February's average maximum daily temperatures to . Temperatures drop significantly in the wetter winters; July's average maximum temperature is . Apart from springs in Water Gully, the site of Newman's Nursery ruins, all of the numerous creeks in the park are seasonal and dry for much of the year. The park rises from approximately above mean sea level on its western side to at the highest point in the park's southeast corner. Most of the park is steeply sloping with gradients steeper than one in four. Except for the base of Water Gully, topsoil throughout the park is shallow and low in plant nutrients. There are frequent serious bushfires in the park. Much of the reserve was burned in 1980, eastern parts burned in 1981, and most of the park burned again in the 1983 Ash Wednesday fires; Newman's Nursery's remains were devastated during the 1983 bushfire. As recently as 2004, a major fire burned over of bushland next to Anstey Hill. Most fires in the park are deliberately lit and the park is regarded as a "hotspot" for arson. Arson in the park is not a recent phenomenon; an early record comes from an 1869 coronial inquiry. The park has more than one arson attack, on average, each year. In the hill's face, encompassing Anstey Hill, approximately 60% of all fires (1999–2004) are deliberately lit and less than 5% are classed as naturally occurring. Most deliberately lit fires begin at the park's boundaries and are contained within it. Geology Elevation rise across the park results from land uplift along the Burnside-Eden fault zone. This zone is a major land fault separating the Adelaide Plains from the Mount Lofty Ranges and runs north-north-east across the park from its southwest corner. The park is underlain by neoproterozoic sedimentary rocks of the Burra Group overlying a Precambrian crystalline basement. Sediments were formed approximately 700 million years ago (mya) from sand washed into a shallow sea. Sand layers were then folded and slightly metamorphosed during the delamerian orogeny, a period of mountain building caused by tectonic plate movements and resulting east–west compression of Australia. This pushed up a mountain range, on the site of the present Mount Lofty Ranges, approximately 450 mya. The range was eroded to a level plain over the following 350