1 00:00:00,000 --> 00:00:03,000 I'm here at VIMS with Ms. Masellus. 2 00:00:03,000 --> 00:00:06,000 She's showing me the vessels they use to map and take core samples. 3 00:00:06,000 --> 00:00:09,000 We learned that there are mountains and valleys on the ocean floor 4 00:00:09,000 --> 00:00:11,000 and that there's natural oil seepage. 5 00:00:11,000 --> 00:00:14,000 We need to know more about the topography of the ocean. 6 00:00:14,000 --> 00:00:16,000 Can you tell me exactly what the floor looks like? 7 00:00:16,000 --> 00:00:17,000 It's magnificent. 8 00:00:17,000 --> 00:00:19,000 Under the ocean, you can find the tallest mountains, 9 00:00:19,000 --> 00:00:22,000 the deepest valleys, and the flattest plains on Earth. 10 00:00:22,000 --> 00:00:26,000 Sounds fascinating, but I don't see any mountains or valleys when I swim. 11 00:00:26,000 --> 00:00:29,000 That's because where you swim is actually the continental shelf. 12 00:00:29,000 --> 00:00:31,000 This area is located along the edge of the continent 13 00:00:31,000 --> 00:00:34,000 and can extend 10 to 200 kilometers offshore. 14 00:00:34,000 --> 00:00:36,000 So are mountains the next area? 15 00:00:36,000 --> 00:00:38,000 No. Next comes the continental slope. 16 00:00:38,000 --> 00:00:42,000 It starts at the edge of the shelf and dips steeply until you reach the abyssal plain, 17 00:00:42,000 --> 00:00:44,000 which is one of the flattest areas on Earth. 18 00:00:44,000 --> 00:00:47,000 And the next area is where the tallest mountains are, right? 19 00:00:47,000 --> 00:00:51,000 Right. In the middle of the ocean, there are mountain ridges called mid-ocean ridges. 20 00:00:51,000 --> 00:00:55,000 This is where the seafloor is spreading apart, making new seafloor and building mountains. 21 00:00:55,000 --> 00:00:59,000 I learned about the seafloor spreading apart in the case of the shaky quake 22 00:00:59,000 --> 00:01:01,000 when we learned about plate tectonics. 23 00:01:01,000 --> 00:01:06,000 Very good. You'll also find volcanoes over those ridges and over hot spots in the Earth's crust. 24 00:01:06,000 --> 00:01:10,000 If a volcano grows tall enough to rise above sea level, they form islands. 25 00:01:10,000 --> 00:01:14,000 Just like the Hawaiian Islands. Didn't they form over a hot spot? 26 00:01:14,000 --> 00:01:18,000 That's right. And if a volcano doesn't break the surface of the water, then it's called a seamount. 27 00:01:18,000 --> 00:01:19,000 There are also deep ocean trenches. 28 00:01:19,000 --> 00:01:21,000 I always thought of the ocean as sandy. 29 00:01:21,000 --> 00:01:24,000 Under the ocean is a whole world just waiting to be discovered. 30 00:01:24,000 --> 00:01:25,000 And that's where the core samples come in. 31 00:01:25,000 --> 00:01:28,000 Why do you take core samples of the ocean floor? 32 00:01:28,000 --> 00:01:33,000 Seismic reflection images show buried ancient river channels located near here during the last ice age. 33 00:01:33,000 --> 00:01:35,000 Coring helps us to verify that they exist. 34 00:01:35,000 --> 00:01:38,000 It seems like we have another mystery, and we need your help. 35 00:01:38,000 --> 00:01:39,000 Sure thing. What can I do? 36 00:01:39,000 --> 00:01:43,000 Right now, we're trying to find out where the oil globs on our beach came from. 37 00:01:43,000 --> 00:01:47,000 Mr. Wells said that oil sometimes seeps out naturally from the ocean, 38 00:01:47,000 --> 00:01:49,000 so we need to learn more about oil seeps. 39 00:01:49,000 --> 00:01:53,000 Oil and gas can seep directly onto the surface of the earth or into the oceans. 40 00:01:53,000 --> 00:01:55,000 Are seeps very common? 41 00:01:55,000 --> 00:01:56,000 Yes, they're quite common. 42 00:01:56,000 --> 00:02:02,000 Did you know in California, every oil and gas field discovered between 1860 and the early 1900s 43 00:02:02,000 --> 00:02:05,000 was actually found by people seeing it seep up from the earth? 44 00:02:05,000 --> 00:02:07,000 So how does oil and gas seep out? 45 00:02:07,000 --> 00:02:11,000 Seeps can come from a single point or from as many as 30,000 individual little holes. 46 00:02:11,000 --> 00:02:15,000 Divers describe high seepage areas as looking like a whole bunch of gopher holes. 47 00:02:15,000 --> 00:02:17,000 How much oil and gas seeps out? 48 00:02:17,000 --> 00:02:21,000 It varies from place to place and can range from nearly impossible to detect 49 00:02:21,000 --> 00:02:24,000 to thick oil films with globular deposits called tar balls. 50 00:02:24,000 --> 00:02:26,000 That sounds like what's on our beach. 51 00:02:26,000 --> 00:02:30,000 We learned that most of the oil seepage occurs along the Gulf of Mexico, 52 00:02:30,000 --> 00:02:33,000 so we thought that a current could be carrying the oil globs to our beach. 53 00:02:33,000 --> 00:02:38,000 But we learned that there aren't any currents that carry things to Virginia from the Gulf of Mexico. 54 00:02:38,000 --> 00:02:39,000 What about the Gulf Stream? 55 00:02:39,000 --> 00:02:43,000 We know that the Gulf Stream flows northward from the central part of the Atlantic Ocean 56 00:02:43,000 --> 00:02:46,000 and turns back towards Europe up around Canada. 57 00:02:46,000 --> 00:02:48,000 So I don't think that's the answer. 58 00:02:48,000 --> 00:02:50,000 You might want to learn more about the Gulf Stream. 59 00:02:50,000 --> 00:02:52,000 You're right. Maybe it is the Gulf Stream. 60 00:02:52,000 --> 00:02:54,000 Thanks, Ms. Vassalos. 61 00:02:54,000 --> 00:02:56,000 You're welcome. It's my pleasure to help out the treehouse detectives. 62 00:02:56,000 --> 00:02:58,000 Let me show you something else.