In addition to providing polarity data, like those you interpreted in Part B, most terrestrial lava flows contain minerals that can be precisely dated using radiometric age-dating techniques. The combination of these two types of data from a large number of lava flows enables the creation of a polarity timescale, where intervals of normal and reverse polarity can be assigned numerical age ranges. These terrestrial timescales can be applied to oceanic rocks, where magnetic polarity readings can be taken rather cheaply using shipboard equipment (magnetometers), but obtaining samples for radiometric dating is far more difficult.

 As a North American paleomagneticist, you have been tasked with assigning ages to oceanic rocks around the Juan de Fuca ridge based on the shipboard magnetometer readings of seafloor polarity and a magnetic polarity timescale below.  

Use values from the magnetic polarity timescale to assign ages to the oceanic rocks surrounding the Juan de Fuca Ridge. The position of the active ridge is indicated with a thick red line.

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Drag the appropriate labels to their respective targets. Labels may be used more than once. ▸ Hints 0.00 0.78 2.60 Intensity of magnetization Normal Reverse 0.00 Age (millions of years) Juan de Fuca Ridge Isotopic age (millions of years) 0.62 0.75 0.94 O 1.02. 1.26 O 1.37 O 1.68 O 1.74. 1.92 2.12 O 2.29 O 2.51 O 2.67 3.01 -> 3.25 O Lava flows 3.42. 3.52. Reverse polarity O Normal polarity Age (millions of years) -0.00 Shipboard measurement of seafloor magnetic polarity provides seafloor age. Magnetic polarity ti -0.78 -0.99 1.07 -3.04 -3.33 -3.58 b Age and polarity determined for field samples -1.79 -1.95 -2.60 Drag the appropriate labels to their respective targets. Labels may be used more than once. ▸ Hints 0.00 0.78 2.60 Intensity of magnetization Normal Reverse 0.00 Age (millions of years) Juan de Fuca Ridge Isotopic age (millions of years) 0.62 0.75 0.94 O 1.02. 1.26 O 1.37 O 1.68 O 1.74. 1.92 2.12 O 2.29 O 2.51 O 2.67 3.01 -> 3.25 O Lava flows 3.42. 3.52. Reverse polarity O Normal polarity Age (millions of years) -0.00 Shipboard measurement of seafloor magnetic polarity provides seafloor age. Magnetic polarity ti -0.78 -0.99 1.07 -3.04 -3.33 -3.58 b Age and polarity determined for field samples -1.79 -1.95 -2.60 Drag the appropriate labels to their respective targets. Labels may be used more than once. ▸ Hints 0.00 0.78 2.60 Intensity of magnetization Normal Reverse 0.00 Age (millions of years) Juan de Fuca Ridge Isotopic age (millions of years) 0.62 0.75 0.94 O 1.02. 1.26 O 1.37 O 1.68 O 1.74. 1.92 2.12 O 2.29 O 2.51 O 2.67 3.01 -> 3.25 O Lava flows 3.42. 3.52. Reverse polarity O Normal polarity Age (millions of years) -0.00 Shipboard measurement of seafloor magnetic polarity provides seafloor age. Magnetic polarity ti -0.78 -0.99 1.07 -3.04 -3.33 -3.58 b Age and polarity determined for field samples -1.79 -1.95 -2.60 Drag the appropriate labels to their respective targets. Labels may be used more than once. ▸ Hints 0.00 0.78 2.60 Intensity of magnetization Normal Reverse 0.00 Age (millions of years) Juan de Fuca Ridge Isotopic age (millions of years) 0.62 0.75 0.94 O 1.02. 1.26 O 1.37 O 1.68 O 1.74. 1.92 2.12 O 2.29 O 2.51 O 2.67 3.01 -> 3.25 O Lava flows 3.42. 3.52. Reverse polarity O Normal polarity Age (millions of years) -0.00 Shipboard measurement of seafloor magnetic polarity provides seafloor age. Magnetic polarity ti -0.78 -0.99 1.07 -3.04 -3.33 -3.58 b Age and polarity determined for field samples -1.79 -1.95 -2.60