Earth’s ocean is the defining feature of our planet. In the elementary grades students learn that the ocean contains most of Earth’s available water, covers much of Earth’s surface, supports a variety of ecosystems and organisms, shapes landforms, and influences climate. Most students have some firsthand or virtual familiarity with one of the three ocean basins that border the United States—the Atlantic Ocean, Pacific Ocean, or the Gulf of Mexico. When they think of these “oceans,” do they think of a physically separated body of water or part of one larger system made up of one ocean?

The Ocean Literacy Project was established in 2005 to define what students and adults should know about our ocean planet. An Ocean Literacy Framework with seven principles and a K–12 scope and sequence was developed to support ocean literacy. It complements the Next Generation Science Standards disciplinary core idea ESS2.A Earth Systems (NRC 2012) by describing what elementary students in grades K–2 and 3–5 should know about Earth’s ocean. Principle #1 of the Ocean Literacy Framework states: “The Earth has one big ocean with many features” (Ocean Literacy Network 2005). To understand this principle, students should have the opportunity to observe, using a model such as a map, that there are oceans and seas with different names located throughout the world, yet they are all interconnected as one ocean. They also learn that the water moves freely throughout this one large ocean.

Research by Feller (2007) revealed the common misconception, held by both children and adults, that the oceans are not connected and act alone. The formative assessment probe, “How Many Oceans and Seas?” reveals whether students understand the concept of “one ocean” and provides instructional suggestions to develop this important concept (Keeley and Tucker 2016). The best answer is Alejandra: “I think there is really only one ocean because water flows through all of them.” Initially, one of the other answer choices may make more sense to the students, particularly if they connect their geographic knowledge of the different names of oceans and seas, which may imply to students that oceans are separate bodies of water. They may have even heard the term seven seas, which has historically meant the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian, and Southern Oceans. The language we use influences students’ thinking as we typically use the plural oceans when talking collectively about ocean basins. Furthermore, students’ ideas about one ocean are further muddled by the labels we use to label areas of Earth’s ocean such as ocean, sea, gulf, or strait. These geographic terms may imply that these are physically separate and distinct bodies of water. Although the ocean basins have different names, all ocean water can move freely around the globe and mix with other named ocean basins. The core disciplinary idea for grades 3–5, in ESS2.A Earth Systems, refers to Earth’s ocean (singular), not oceans (plural), further reinforcing the idea of one ocean.

Why is it important to uncover the idea of one ocean in the elementary grades? It is important for students and adults to grasp the concept of “one ocean” to understand the global movement of matter and the flow of energy throughout the world’s ocean. Throughout the ocean, there is one interconnected circulation system powered by the wind, tides, the force of Earth’s rotation, the Sun, and water density differences. The shape of ocean basins and adjacent land masses influence the path of circulation. This “global ocean conveyor belt” moves water throughout all of the ocean’s basins, transporting energy (heat), matter, and organisms around the ocean (Ocean Literacy Network 2015). Although these ideas will be developed primarily in middle school, the elementary grades are the time to establish the foundational idea that there is one large, interconnected ocean and that ocean water can move freely throughout the ocean.

After eliciting students’ initial ideas, plan instruction that will provide students with the evidence they need to revisit the probe and use the concept of “one ocean” to revise their initial thinking. Using a model, preferably a large, inflated globe, have students put their finger on a part of the Pacific or Atlantic Ocean. Then have them trace paths that their finger (representing the water) travels throughout the world without crossing over any landforms, ending up where they started. How many different routes can they find? What named oceans and seas did their “water” pass through? Using evidence from their models, students can now revisit the probe and provide an explanation to support the concept of “one ocean.”

This is a reminder that probes should always be used twice. First, to understand what your students are thinking so that you can plan targeted instruction to address their ideas. Simultaneously, the probes activate student thinking and create a desire to learn more. After students have had the opportunity to learn and have gathered the evidence and information they need to revise or solidify their thinking, they revisit the probe, demonstrating the extent to which they can use scientific evidence and principles to explain a concept or phenomenon. And furthermore, the probes provide a powerful metacognitive moment when students recognize how and why their thinking has changed.

Page Keeley (pagekeeley@gmail.com) is a science education consultant and the author of the Uncovering Student Ideas in Science series (http://uncoveringstudentideas.org)