Planetary Geology on Earth: Hilsea Lines or Mars EarthCache

This valuable nature area has developed on a site that originally served as a military base.  The first defences were built in 1544 to protect the naval interests from an inland attack and further established in 1757 south of Ports Creek.  They remained largely unaltered for over 100 years before the existing Lines replaced them in 1871 when the renewed threat of a French invasion prompted the need for stronger defences.  This 2 mile long structure consisted of ramparts 9m high and 20m wide, with six Bastions of bombproof casemates and a moat to the north.  The expected invasion did not materialise and the Lines were never used in battle.  Some changes took place early 20th Century, but most of the original structure is unaltered.  The Lines were designated a Scheduled Ancient Monument in 1964 and the site was given Conservation Area status in 1994 in recognition of the value, not only of the monument, but also of its setting.

8 interpretation boards have been erected across the site to illustrate the varied self-guided walks that can be enjoyed to appreciate the significance of the military and natural history on offer. Substantial restoration works were made to Hilsea Lines in 2001-02 as part of a Heritage Lottery Fund project to return some of the Bastions to their original appearance and further enhance the area.

There is a Countryside Ranger based on site at one of the restored casemates, who is on hand to oversee the day-to-day care and protection of this Conservation Area and runs a healthy volunteers programme for those interested in participating with the valuable conservation and restoration tasks.

The Rock that makes up the land feature on the North horizon was laid down between 100 and 65 million years ago at the bottom of a deep tropical sea. This particular rock is made from the compressed skeletons of countless millions of marine algae called coccospheres. The same layer reappears to the north where it forms the South Downs, and again to the south where it forms the rock* outcrops on the Isle of Wight. It is overlain by more recent deposits such as Reading Beds and London Clay. A combination of movements in the earth's crust caused the feature to be pushed up about 20 million years ago, following the lines of weakness of much deeper ancient faults. These faults may still cause occasional earth tremors today The fossil remains of sea urchins and other creatures have been unearthed from the rock that forms this feature and it proves that it was formed in marine waters several hundred feet deep, and the fact that once formed this land feature has never been re-submerged after subsequent Ice Ages makes it a geologically unique feature.

New Mars Global Surveyor images reveal sedimentary rock layers on the Red Planet that may have formed underwater in the distant martian past. "We see distinct, thick layers of rock within craters and other depressions for which a number of lines of evidence indicate that they may have formed in lakes or shallow seas. We have never before had this type of irrefutable evidence that sedimentary rocks are widespread on Mars," said Dr. Michael Malin, principal investigator for the Mars Orbiter Camera on NASA's Mars Global Surveyor spacecraft at Malin Space Science Systems (MSSS), San Diego, CA. "These images tell us that early Mars was very dynamic and may have been a lot more like Earth than many of us had been thinking" Such layered rock structures where there were once lakes are common on Earth. The pancake-like layers of sediment compressed and cemented to form a rock record of the planet's history'