ADrilling down from a position in the ocean, because the crust is much thinner there.
The Earth s mantle is the part of the planet that lies between the crust and the iron ball at its center, and to reach it, would require drilling down from a position in the ocean, because the crust is much thinner there.  The Earth's crust is an extremely thin layer of rock, like the skin of an apple in relative terms. It amounts to less than half of 1 percent of the planet. But the crust is exceptionally important, and not just because we live on it. The crust can be thicker than 80 kilometers in some spots, less than one kilometer in others. Underneath it is the mantle, a layer of rock some 2700 kilometers thick that accounts for the bulk of the Earth. The crust is primarily made of granite and basalt while the mantle beneath is made of peridotite. In the mid-ocean, the thickness of the crust can be as little as 5 km. The entire crust occupies just 1% of the Earth’s volume. The crust is composed of a variety of igneous, metamorphic and sedimentary rocks gathered together into tectonic plates. These plates float above the Earth’s mantle, and it’s believed that convection of rock in the mantle causes the plates to slide around.  ] layers: inner core, outer core, mantle [mantle: A zone of hot rock in the interior of the Earth, located between the outer crust and the molten core. ] and crust [crust: The outer layer of the Earth, on top of the mantle. It is between 6 and 48 kilometres thick and includes the continents and the ocean floor. ] . 1 The mantle is made up of semi-molten rock called magma. 2  In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt. 3  The crust is the outer layer of the earth. 4  It is a thin layer between 0-60 km thick. 5  The crust is the solid rock layer upon which we live. The plan is to go right through the Earth's crust, the rocky top layer of the planet, which is 18 to 37 miles (30 to 60 kilometers) thick on land, but as little as 3 miles (5-kilometers) thick at its thinnest spots on the ocean floor [source: Osman ].  Earths Crust. Introduction. The Earths crust is the outermost layer of our planet and is less than 1% of the Earth's volume. The crust and the mantle contain different kinds of rocks making them chemically different. The upper mantle rocks are primarily peridotite. The crust contains of a variety of rocks.  It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). These plates usually move along smoothly but sometimes they stick and build up pressure. The pressure builds and the rock bends until it snaps. When this occurs an Earthquake is the result! Notice how thin the crust of the Earth is in comparison to the other layers. The seven continents and ocean plates basically float across the mantle which is composed of much hotter and denser material What's Down There. The Earth's radius is about 4,000 miles (6,400 kilometers). The main layers of its interior are in descending order: crust, mantle and core. The crust thickness averages about 18 miles (30 kilometers) under the continents, but is only about 3 miles (5 kilometers) under the oceans. It is light and brittle and can break. Scientist said this week they had drilled into the lower section of Earth's crust for the first time and were poised to break through to the mantle in coming years. The Integrated Ocean Drilling Program (IODP) seeks the elusive Moho, a boundary formally known as the Mohorovicic discontinuity.
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how to get through the Earth's crust